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Questions and Answers
In a frequency distribution table, which column represents the percentage of scores at or below a certain value?
In a frequency distribution table, which column represents the percentage of scores at or below a certain value?
- Cumulative Frequency
- Proportion
- Percentage
- Cumulative Percentage (correct)
For a skewed distribution, why is the mean often not the best measure of central tendency?
For a skewed distribution, why is the mean often not the best measure of central tendency?
- It always equals the median in a skewed distribution.
- It is not affected by extreme scores.
- It accurately represents the most frequent score.
- It is pulled in the direction of the tail by extreme scores. (correct)
When calculating variance as a population parameter versus estimating it from a sample, what is the key difference in the formula?
When calculating variance as a population parameter versus estimating it from a sample, what is the key difference in the formula?
- The population formula calculates the square root.
- There is no difference in the formulas.
- The population formula uses N in the denominator, whereas the sample formula uses N-1. (correct)
- The sample formula uses N in the denominator, whereas the population formula uses N-1.
Given a population with µ = 50 and σ = 5, what z-score corresponds to a score of X = 40?
Given a population with µ = 50 and σ = 5, what z-score corresponds to a score of X = 40?
A score is 15 points above the mean in a distribution where the standard deviation is 5. What is the corresponding z-score?
A score is 15 points above the mean in a distribution where the standard deviation is 5. What is the corresponding z-score?
In a psychology class of 40 females and 20 males, what is the probability that a randomly selected student is male?
In a psychology class of 40 females and 20 males, what is the probability that a randomly selected student is male?
For a population with µ = 60 and σ = 8, what is the standard error of the mean for samples of n = 16?
For a population with µ = 60 and σ = 8, what is the standard error of the mean for samples of n = 16?
Suppose the average self-esteem score of adolescents is 50 with a standard deviation of 10. A sample of 25 adolescents who participate in sports has a mean self-esteem score of 54. Compute the z-score for the sample mean.
Suppose the average self-esteem score of adolescents is 50 with a standard deviation of 10. A sample of 25 adolescents who participate in sports has a mean self-esteem score of 54. Compute the z-score for the sample mean.
A researcher conducts a hypothesis test with α = 0.05. What does this alpha level represent?
A researcher conducts a hypothesis test with α = 0.05. What does this alpha level represent?
A company implements a wellness program and wants to determine if it reduces employee absences. They conduct a one-tailed hypothesis test. What is the primary focus of a one-tailed test in this scenario?
A company implements a wellness program and wants to determine if it reduces employee absences. They conduct a one-tailed hypothesis test. What is the primary focus of a one-tailed test in this scenario?
Flashcards
What is a Histogram?
What is a Histogram?
A graph showing the frequency distribution of numerical data.
What is the Mean?
What is the Mean?
The sum of the scores divided by the number of scores.
What is the Median?
What is the Median?
The middle score in a distribution when the scores are arranged in order.
What is the Mode?
What is the Mode?
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What is a skewed distribution and why is the mean not always a good measure of the central tendency for it?
What is a skewed distribution and why is the mean not always a good measure of the central tendency for it?
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What is SS?
What is SS?
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What is standard deviation?
What is standard deviation?
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What is a z-score?
What is a z-score?
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What is Random Sampling?
What is Random Sampling?
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Study Notes
- These notes cover psychological statistics practice problems from Chapters 2 through 9.
Chapter 2
- Construct a frequency distribution table for the test scores, including columns for proportion, percentage, cumulative frequency (cf), and cumulative percentage (c%).
- The test scores for frequency distribution are: 85, 85, 95, 75, 55, 65, 85, 75, 55, 65, 85, 95, 85, 65, 75, 95, 75, 85, 85, 95
- Sketch a Histogram for the distribution of scores.
- Determine the total number of scores for the distribution shown in the frequency distribution table.
Chapter 3
- Calculate the mean, median, and mode for the sample scores: 7, 5, 6, 6, 3, 4, 6, 3, 6, 5, 4, 2
- Explain why the mean is often not a good measure of central tendency for a skewed distribution.
Chapter 4
- Calculate the sum of squares (SS), variance, and standard deviation for the following N = 6 scores: 6, 4, 3, 4, 5, 2
- Complete the calculations treating the scores as a population.
- Complete the calculations treating the scores as a sample.
Chapter 5
- Given a population with µ = 40 and σ = 4, calculate the z-score for each X value:
- X = 42
- X = 48
- X = 38
- X = 36
- X = 32
- X = 50
- Given a population with µ = 40 and σ = 4, find the score (X value) that corresponds to each z-score:
- z = 1.00
- z = 0.75
- z = 1.50
- z = -0.50
- z = -0.25
- z = -1.50
- A score 10 points below the mean corresponds to a z-score of -0.50; determine the population standard deviation.
Chapter 6
- A psychology class has 34 females and 16 males and names are randomly selected
- Find the probability that the first student selected is female.
- If 3 students are randomly selected without replacement and the first two are female, find the probability that the third student is male.
Chapter 7
- For a population with µ = 80 and σ = 12, find the expected error on average between the sample mean (M) and the population mean for the sample sizes:
- n = 4
- n = 16
- n = 36
- Given a population with µ = 70 and σ = 20, calculate the z-score corresponding to each sample mean:
- M = 75 for a sample of n = 4 scores
- M = 75 for a sample of n = 16 scores
- M = 75 for a sample of n = 25 scores
Chapter 8
- A study with n = 100 adolescents who have a history of group participation is given a self-esteem questionnaire with a mean of M = 43.84.
- The general population of adolescents scores have a normal distribution with µ = 40 and σ = 12.
- Determine if the sample provides enough evidence to conclude that self-esteem scores for group-affiliated adolescents are significantly different from the general population, using a two-tailed test with α = .01.
Chapter 9
- The average number of absences in January and February last year was µ = 7.4
- This year, a sample of n = 100 people took flu shots, with an average absence of M = 4.2 and s = 2.
- Determine if these data indicate a significant reduction in absences, using a one-tailed test with α = .05.
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