AP Statistics Chapter 6 Quiz

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Questions and Answers

What does the standardized test statistic rely on when comparing a statistic to a parameter?

  • Standard deviation of the parameter
  • Standard error of the statistic (correct)
  • Mean of the statistic
  • Critical value of the parameter

Which formula correctly represents the confidence interval calculation?

  • Statistic × (critical value) × standard error of the statistic
  • Statistic ± (critical value) × standard error of the statistic (correct)
  • Statistic + (critical value) × standard error of the statistic
  • Statistic ± (critical value) / standard error of the statistic

In a Chi-square statistic calculation, what does the symbol χ² represent?

  • The ratio of observed to expected frequencies
  • The average of expected frequencies
  • The difference between observed and expected frequencies (correct)
  • The sum of squared differences between expected frequencies

What is the primary purpose of calculating a confidence interval?

<p>To estimate the range within which the population parameter lies (D)</p> Signup and view all the answers

What relationship does the standard error of the statistic have with sample size?

<p>It decreases as the sample size increases (D)</p> Signup and view all the answers

What is the probability that a randomly selected household in Tower Hill has at least two cell phones?

<p>0.70 (B)</p> Signup and view all the answers

Which statement is true about binomial and geometric random variables?

<p>A geometric setting allows for more than two outcomes for each trial. (C)</p> Signup and view all the answers

What is the probability that the basketball player makes at least two of her three free throws if she makes 80% of her shots?

<p>0.896 (B)</p> Signup and view all the answers

In the distribution of household cell phones, what is the probability of a household having zero cell phones?

<p>0.1 (A)</p> Signup and view all the answers

If a geometric random variable has a success probability of 0.85, how is its distribution characterized?

<p>It is skewed to the left. (C)</p> Signup and view all the answers

How many total households' phone data are provided in the probability distribution for Tower Hill?

<p>6 (B)</p> Signup and view all the answers

What does the geometric setting assume about the trials?

<p>Each trial must be independent. (A)</p> Signup and view all the answers

For the basketball player, what is the probability of making exactly one free throw out of three attempts?

<p>0.192 (D)</p> Signup and view all the answers

What type of statistical setting is being described when selecting individuals until finding an HIV-positive person?

<p>Geometric setting (C)</p> Signup and view all the answers

In the context of selecting policewomen and policemen, what does the height probability distribution indicate?

<p>Heights are normally distributed with different means and standard deviations. (A)</p> Signup and view all the answers

How many individuals would you expect to select to find the first HIV-positive person if the prevalence is 1%?

<p>100 (A)</p> Signup and view all the answers

What is the primary reason the selection of height measurements does not form a geometric or binomial setting?

<p>Each trial has a different probability of success. (B)</p> Signup and view all the answers

What percentage of respondents in an online poll subscribe to the 'five-second rule'?

<p>20% (B)</p> Signup and view all the answers

What assumption can be made about the population when conducting the selection of individuals in a geometric setting with a 1 in 100 prevalence?

<p>The population is larger than 1000. (B)</p> Signup and view all the answers

If the mean height of policewomen is 65 inches and the mean height of policemen is 70 inches, what concept does this illustrate?

<p>A normal distribution with different means (C)</p> Signup and view all the answers

Why is it important to indicate the methods used in selecting individuals for a study?

<p>To verify the randomness of the selection process. (D)</p> Signup and view all the answers

What is the expected value of the daily profit X for Jocelyn's babysitting business?

<p>$13.5 (A)</p> Signup and view all the answers

If a bottling machine improperly caps 5% of bottles, what is the probability of exactly 2 improperly capped bottles in a sample of 20?

<p>0.19 (B)</p> Signup and view all the answers

What is the probability of rolling exactly 3 sevens in 10 rolls of an 8-sided die?

<p>0.0439 (A)</p> Signup and view all the answers

Sharon has mp3 files with a mean size of 4.0 MB and standard deviation of 1.8 MB. What is likely to be the mean size of 10 randomly selected songs?

<p>40 MB (B)</p> Signup and view all the answers

To fit a geometric distribution, what must the random variable X ensure?

<p>The probability of success is constant. (B)</p> Signup and view all the answers

Which of these values indicates a correct application of the probability mass function to find the probability of exactly 2 successes?

<p>0.19 (B)</p> Signup and view all the answers

In creating a mixtape, how are the songs' lengths typically estimated from their file sizes?

<p>Length = 1.07(file size) - 0.02 (B)</p> Signup and view all the answers

What is the correct interpretation of a probability of 0.19 when dealing with the scenario of improperly capped bottles?

<p>19% chance exactly 2 bottles will be improperly capped. (D)</p> Signup and view all the answers

What is the formula for the mean of a discrete random variable X?

<p>$ ext{E}(X) = ext{µ}_X = ext{Σ} x_i ⋅ P(x_i)$ (A)</p> Signup and view all the answers

For a binomial distribution, which of the following statements is true about the parameters identified as n and p?

<p>n represents the number of trials and p represents the probability of success. (D)</p> Signup and view all the answers

What does the standard deviation σX express in a probability distribution?

<p>The dispersion of the random variable around the mean. (B)</p> Signup and view all the answers

Which formula correctly represents the probability of a specific outcome x in a binomial distribution?

<p>$P(X = x) = \frac{n!}{x!(n-x)!} p^x (1-p)^{n-x}$ (A)</p> Signup and view all the answers

How is the mean for a geometric distribution defined?

<p>$ ext{µ}_X = \frac{1}{p}$ (A)</p> Signup and view all the answers

Which of the following is NOT a characteristic of the binomial distribution?

<p>The trials are dependent on each other. (C)</p> Signup and view all the answers

What does the notation $P(X = x)$ imply in probability distributions?

<p>The probability that variable X takes on the value exactly equal to x. (D)</p> Signup and view all the answers

In a discrete probability distribution, how is the variance calculated?

<p>$ ext{Var}(X) = Σ P(x_i)(x_i - µ_X)^2$ (A)</p> Signup and view all the answers

What is the mean of the sampling distribution for a single population proportion, p̂?

<p>$p$ (D)</p> Signup and view all the answers

In the context of two populations, what does the symbol p̂c represent?

<p>The combined sample proportion (C)</p> Signup and view all the answers

What is the standard error for the difference in sample proportions, p̂1 - p̂2?

<p>$ rac{p̂_1(1 - p̂_1)}{n_1} + rac{p̂_2(1 - p̂_2)}{n_2}$ (A)</p> Signup and view all the answers

What does the symbol μX indicate in sampling distributions for means?

<p>The mean of the sampling distribution (D)</p> Signup and view all the answers

For two populations, what is the formula for the standard error of X1 and X2?

<p>$ rac{s_{12}}{n_1} + rac{s_{22}}{n_2}$ (A)</p> Signup and view all the answers

Which equation represents the standard error of the sample mean for one population?

<p>$ rac{s}{n}$ (D)</p> Signup and view all the answers

What does the symbol μb represent in the context of simple linear regression?

<p>The expected value of the slope (D)</p> Signup and view all the answers

What is the formula used to calculate the standard error of the slope in simple linear regression?

<p>$ rac{s_{y}}{s_{x} imes n }$ (A)</p> Signup and view all the answers

In sampling distributions, which term describes the measure of variability from the theoretical population?

<p>Standard deviation (A)</p> Signup and view all the answers

Which of the following statements is true regarding standard error?

<p>It decreases as the sample size increases. (A)</p> Signup and view all the answers

What is the formula for the variance of the difference in sample means for two populations?

<p>$ rac{s_1^2}{n_1} + rac{s_2^2}{n_2}$ (A)</p> Signup and view all the answers

When assuming both population proportions are equal, which of the following formulas is correct for the standard error of p̂1 - p̂2?

<p>$p̂_c (1 - p̂_c) rac{1}{n_1} + rac{1}{n_2}$ (D)</p> Signup and view all the answers

Flashcards

Geometric Distribution

A probability distribution that describes the number of trials required to achieve the first success in a sequence of independent Bernoulli trials. It is characterized by a constant probability of success in each trial.

Binomial Distribution

A probability distribution that describes the number of successes in a fixed number of independent Bernoulli trials. It is characterized by a constant probability of success in each trial.

Constant Probability of Success

In a geometric setting, the probability of success is constant for each trial.

Independent Trials

In a geometric setting, each trial is independent of the others. The outcome of one trial doesn't affect the outcomes of other trials.

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Geometric Random Variable

A variable that represents the number of trials needed to achieve the first success in a sequence of independent Bernoulli trials.

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Binomial Random Variable

A random variable that represents the number of successes in a fixed number of independent Bernoulli trials.

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Bernoulli Trial

A trial where there are only two possible outcomes - success or failure.

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Normal Distribution

The distribution of a continuous random variable where the probability density function is bell-shaped.

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Probability of at least two cell phones

The probability of a household having at least two cell phones is the sum of the probabilities of having 2, 3, 4, or 5 cell phones.

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Binomial vs. Geometric

The geometric setting involves repeated trials until success is achieved, while the binomial setting involves a fixed number of trials.

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Skewness in Geometric Distribution

If the probability of success is closer to 1, the distribution will be skewed to the left since it's more likely to succeed early on.

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Probability of at least two successful free throws

The probability of making at least two out of three free throws is the sum of the probabilities of making exactly two and making all three free throws.

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Binomial Probability Formula

The probability of exactly k successes in n independent trials, each with the same probability of success p, is given by the binomial probability formula.

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Expected Value of a Binomial Random Variable

The expected value of a binomial random variable is the product of the number of trials and the probability of success on each trial.

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What is the expected value of a random variable?

The expected value of a random variable represents the average value you would expect to obtain if you were to repeat the experiment many times.

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How is the expected value calculated?

The expected value of a discrete random variable is calculated by multiplying each possible outcome by its probability and summing the results.

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What is a binomial distribution?

A binomial distribution describes the probability of getting a certain number of successes in a fixed number of trials, where each trial has only two possible outcomes (success or failure) and the probability of success is constant.

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How is the probability of exactly k successes in n trials calculated?

The binomial probability formula calculates the probability of getting exactly k successes in n trials, where the probability of success on each trial is p. The formula uses combinations to account for different orderings.

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What is the expected value of a geometric distribution?

The expected value of a geometric distribution represents the average number of trials needed to get the first success. It's the reciprocal of the probability of success on a single trial.

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What is a geometric distribution?

A geometric distribution describes the probability of the number of trials it takes to get the first success in a sequence of independent trials, where each trial has only two possible outcomes (success or failure) and the probability of success is constant.

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What is the mean of a random variable?

The mean of a random variable is its expected value. It measures the central tendency of the distribution.

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What is the standard deviation of a random variable?

The standard deviation of a random variable measures the spread or variability of the distribution around its mean. A larger standard deviation indicates greater spread.

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Conditional Probability (P(A|B))

The probability of event A occurring given that event B has already occurred.

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Probability Distribution

A way to organize all possible values a random variable can take and their corresponding probabilities.

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Mean (µX) of a Discrete Random Variable

The average value of a random variable, calculated by weighting each possible value by its probability.

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Standard Deviation (σX) of a Discrete Random Variable

The spread or variability of a random variable, calculated as the square root of the variance.

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Discrete Random Variable

A random variable that can only take on a finite number of values or a countably infinite number of values.

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Binomial Probability (P(X=x))

The probability of a specific number of successes 'x' in 'n' trials, given a probability of success 'p' on each trial.

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Sampling Distribution

The distribution of sample statistics obtained by repeatedly drawing samples from a population.

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Inferential Statistics

The process of using sample data to draw conclusions about a population.

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Standardized Test Statistic

A standardized measure of how far a sample statistic deviates from a population parameter.

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Confidence Interval

A range of values that is likely to contain the population parameter.

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Chi-Square Test

A statistical test used to compare observed frequencies with expected frequencies.

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Sampling Distribution of Proportions: Mean

The average of all possible sample proportions (p̂) from a population. It's represented by μp̂ and equals the population proportion (p).

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Sampling Distribution of Proportions: Standard Error

Measures the spread or variability of sample proportions around the population proportion (p). It's calculated as √[p(1-p)/n], where n is the sample size.

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Sampling Distribution of Two Proportions (Equal p)

The sampling distribution of the difference between two sample proportions (p̂1 - p̂2) when the population proportions (p1 and p2) are assumed to be equal. It's centered around zero, indicating no difference between the populations.

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Sampling Distribution of Means: One Population

The sampling distribution of the individual sample mean (X̄) for a given population. It's centered around the population mean (μ) and its shape depends on the distribution of the population.

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Sampling Distribution of Means: Standard Error

The standard deviation of the sampling distribution of means, representing the spread of sample means around the population mean. It's calculated as σ/√n, where σ is the population standard deviation and n is the sample size.

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Sampling Distribution of Means: Two Populations

The sampling distribution of the difference between two sample means (X̄1 - X̄2). It's centered around the difference between the population means (μ1 - μ2) and its spread depends on the population variances and sample sizes.

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Sampling Distribution of Regression Slope

The sampling distribution of the estimated slope coefficient (b) in a simple linear regression model. It's centered around the true population slope (β) and its spread depends on the sample size and variability of the independent variable.

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Sampling Distribution of Regression Slope: Standard Error

The standard deviation of the sampling distribution of the estimated slope coefficient (b), representing the spread of slope estimates around the true population slope (β). It's calculated as s/(√n * sx) where s is the standard error of the regression, n is the sample size, and sx is the standard deviation of the independent variable.

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Sampling Distribution of Proportions (Overview)

A probability distribution that describes the entire collection of possible sample proportions (p̂) that could be drawn from a population. It helps us understand the likelihood of observing specific sample proportions based on the population proportion (p) and sample size.

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Sampling Distribution of Means (Overview)

A probability distribution that describes the entire collection of possible sample means (X̄) that could be drawn from a population. It helps us understand the likelihood of observing specific sample means based on the population mean (μ) and sample size.

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Population Standard Deviation

The standard deviation of the theoretical population, representing the typical deviation of individual observations from the population mean. It's symbolized by 'σ'. In contrast to the standard error, which refers to the spread of sample statistics.

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Standard Error (General Concept)

The standard deviation of the sampling distribution of a statistic, representing the variability of the statistic across different samples. It's symbolized by 's' and is calculated differently for different statistics (like proportions and means).

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Standard Error of Regression

A statistic that measures the amount of variation in the data around the regression line. It's a measure of the scatter of the data points about the regression line.

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Sampling Distribution of Two Proportions (Unequal p)

The sampling distribution of the difference between two sample proportions (p̂1 - p̂2) when the population proportions (p1 and p2) are not assumed to be equal.

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Sample Data

A set of data points used to estimate the parameters of a statistical model.

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Population Data

A hypothetical population encompassing all possible observations of a variable.

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Study Notes

AP Statistics Chapter 6 Test Notes

  • Question 1: Probability of at least two cell phones. The probability distribution for the number of cell phones in a household is given. To find the probability of at least two cell phones, sum the probabilities for 2, 3, 4, and 5 cell phones.

  • Question 2: True statements about binomial and geometric settings. A binomial setting has a fixed number of trials, and the probability of success remains constant for each trial. A geometric setting counts the number of trials until a success.

  • Question 3: Probability of making at least two free throws. A basketball player makes 80% of her free throws. The problem asks for the probability she makes at least two of three free throws, given independent attempts. Use the binomial probability formula.

  • Question 4: Expected value of daily profit. A babysitting business has a probability distribution for daily profit. To find the expected value, multiply each daily profit by its corresponding probability and sum the results.

  • Question 5: Probability of exactly 2 improperly capped bottles. A bottling machine improperly applies caps to 5% of bottles. Find the approximate probability that exactly 2 caps are improperly applied when selecting 20 bottles randomly. (Use the binomial probability formula).

  • Question 6: Probability of getting exactly 3 sevens in 10 rolls. Calculate the probability of rolling exactly 3 sevens in 10 rolls of an 8-sided die. (Use the binomial probability formula).

  • Question 7: Mean and standard deviation of total megabytes. The mean size of an MP3 song file is 4.0 megabytes, and the standard deviation is 1.8 megabytes. Find the mean and standard deviation of the total size (in megabytes) of 10 randomly selected songs.

  • Question 8: Condition for a geometric distribution. A geometric distribution requires the probability of success to be the same for each trial. The number of trials is not fixed.

  • Question 9: Mean and standard deviation of commute time. Find the mean and standard deviation of a commute that involves the Blue line (mean=18 min, SD=2 min), Red Line (mean=12 min, SD=1 min) and a waiting time (mean=10 min, SD=5 min), assuming independence.

  • Question 10: Probability of needing a tow truck. The probability of drivers carrying jumper cables is 16%. Find the probability of needing to call a tow truck after asking 10 people without success. (Use the geometric probability formula).

  • Question 11: Probability of a report weighing less than 45 grams. The weight of reports in a department follows a normal distribution. Mean = 60 grams, SD =12 grams. Find the probability that the next report weighs less than 45 grams.

  • Question 12: Finding the Expected Number of People to Interview. Find the number of people the reporter needs to interview to find their first Democrat if 60% of adults are registered Democrats.

  • Question 13: Binomial, Geometric, or Neither. Determine whether the random variable described satisfies the conditions for a binomial setting, geometric setting or neither.

  • Question 14: Probability of a policewoman being taller. Suppose height of policemen is normally distributed with mean 70 in and SD 3 in. Policewomen have mean height 65 in. and SD 2.5 inches. Find the probability of a randomly selected policewoman being taller than a randomly selected policeman.

  • Question 15: Probability of subscribing to "five-second rule" . 20% of people subscribe to the 'five-second rule'. Determine the probability that exactly 3 people subscribe in a sample of 15. Find the expected value of this sample. Find the standard deviation of this sample.

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