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# Statistics Unit 2 Flashcards

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descriptive

### A value at the center or middle of a data set is​ a(n) _______.

measure of center

### Which of the following is NOT a measure of center?

• Census (correct)
• Mode
• Mean
• Median
• ### The measure of center that is the value that occurs with the greatest frequency is the​ _______.

<p>mode</p> Signup and view all the answers

### Which of the following is always true?

<p>In a symmetric and bell-shaped distribution, the mean, median, and mode are the same</p> Signup and view all the answers

### If the standard deviation for a set of data is 0, which of the following must be true?

<p>All of the data values are identical</p> Signup and view all the answers

### The Range Rule of Thumb roughly estimates the standard deviation of a data set as _______.

<p>s = range/4</p> Signup and view all the answers

### What is the role of the term average in statistics?

<p>The term average is not used in statistics; the term mean should be used.</p> Signup and view all the answers

### The symbol for sample standard deviation is _______.

<p>s</p> Signup and view all the answers

### The symbol for population standard deviation is _______.

<p>σ</p> Signup and view all the answers

### The symbol for sample variance is _______.

<p>s^2</p> Signup and view all the answers

### The symbol for population variance is _______.

<p>σ^2</p> Signup and view all the answers

### If sample data consist of weights measured in grams, then the unit for sample standard deviation would be _______.

<p>g</p> Signup and view all the answers

### The unit for population standard deviation would be _______.

<p>g</p> Signup and view all the answers

### The unit for sample variance would be _______.

<p>g^2</p> Signup and view all the answers

### The unit for population variance would be _______.

<p>g^2</p> Signup and view all the answers

### For data sets having a distribution that is approximately​ bell-shaped, _______ states that about​ 68% of all data values fall within one standard deviation from the mean.

<p>the Empirical Rule</p> Signup and view all the answers

### The square of the standard deviation is called the _______.

<p>variance</p> Signup and view all the answers

### When a data value is converted to a standardized scale representing the number of standard deviations the data value lies from the​ mean, we call the new value a​ _______.

<p>z-score</p> Signup and view all the answers

### Whenever a data value is less than the​ mean, _______.

<p>the corresponding z-score is negative</p> Signup and view all the answers

### The 5-number summary includes _______.

<p>min, Q1, median, Q3, max</p> Signup and view all the answers

### Which of the following is NOT a value in the 5-number summary?

<p>Mean</p> Signup and view all the answers

### What do P(A) and P(Ā) represent when A denotes the event of selecting someone with blue eyes?

<p>P(A) represents the probability of selecting an adult with blue eyes; P(Ā) represents the probability of selecting an adult who does not have blue eyes.</p> Signup and view all the answers

### Events that are​ _______ cannot occur at the same time.

<p>disjoint</p> Signup and view all the answers

### What does​ P(B|A) represent?

<p>The probability of event B occurring after it is assumed that event A has already occurred.</p> Signup and view all the answers

### Two events A and B are​ _______ if the occurrence of one does not affect the probability of the occurrence of the other.

<p>independent</p> Signup and view all the answers

### ​'At least​ one' is equivalent to​ _______.

<p>'one or more'</p> Signup and view all the answers

### A​ _______ probability of an event is a probability obtained with knowledge that some other event has already occurred.

<p>conditional</p> Signup and view all the answers

### What is the probability of getting the correct Social Security number of the person who was given the​ receipt?

<p>1/100,000</p> Signup and view all the answers

### If radio station call letters must begin with either K or W and must include either two or three additional​ letters, how many different possibilities are​ there?

<p>36504</p> Signup and view all the answers

## Study Notes

### Descriptive Statistics

• Descriptive statistics summarize or describe characteristics of data without making conclusions beyond the data.
• Measures of center include mean, median, and mode.

### Measures of Center

• The measure of center represents the middle value in a data set.
• The mode is the most frequently occurring value, while the census is not a measure of center.
• In a symmetric, bell-shaped distribution, the mean, median, and mode are equal.

### Data Characteristics

• A standard deviation of 0 indicates that all data values are identical.
• The Range Rule of Thumb estimates standard deviation as ( s = \text{range}/4 ).

### Terminology in Statistics

• The term "average" is not used; "mean" refers to the sum of sample values divided by the total number of values.
• Sample standard deviation is symbolized as ( s ), while population standard deviation is represented by ( \sigma ).

### Variance

• The sample variance is denoted by ( s^2 ) and population variance by ( \sigma^2 ).
• Units for standard deviation in grams remain in grams (g), while variance is expressed in square grams (g²).

### Empirical Rule

• According to the Empirical Rule, approximately 68% of data values in a bell-shaped distribution fall within one standard deviation from the mean.

### Standardized Scores

• A z-score indicates how many standard deviations a data value is from the mean; scores below the mean yield negative z-scores.

### Five-Number Summary

• The five-number summary includes minimum, Q1, median, Q3, and maximum values, while the mean is not part of this summary.

### Probability Concepts

• The probability of event A (e.g., selecting someone with blue eyes) is denoted as ( P(A) ) and ( P(\bar{A}) ) represents the probability of the complementary event.
• The addition rule requires careful application to avoid double-counting outcomes.

### Event Relationships

• Disjoint events cannot occur simultaneously, while independent events are unaffected by each other's occurrence.
• Conditional probability ( P(B|A) ) describes the probability of event B occurring given that event A has occurred.

### Probability of Events

• "At least one" is synonymous with "one or more."
• The probability of selecting the correct Social Security number after knowing partial digits is extremely low at ( \frac{1}{100,000} ).

### Combinatorial Probability

• For radio station call letters that start with K or W and have two or three additional letters, there are 36,504 unique combinations possible.

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## Description

Test your knowledge of essential concepts in descriptive statistics with these flashcards. This quiz covers key definitions and measures of center, helping you to better understand how to summarize data. Great for students looking to reinforce their learning in statistics.

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