Statistics in psychology: measures of central tendency and dispersion, normal curve, parametric (t‑test) and non‑parametric tests (sign test, Wilcoxon, Mann–Whitney, Kruskal–Wallis, Friedman), power analysis and effect size. - Question Bank

1. Which of the following is a parametric test used for comparing the means of two related groups?
A) Independent samples t-test
B) Paired samples t-test
C) Mann-Whitney U test
D) Wilcoxon signed-rank test
2. A researcher wants to compare the effectiveness of three different therapies on reducing anxiety levels. The data are ordinal. Which test should be used?
A) Kruskal-Wallis H test
B) Friedman test
C) One-way ANOVA
D) Independent samples t-test
3. Which of the following is a measure of dispersion?
A) Mode
B) Median
C) Range
D) Mean
4. When comparing more than two independent groups with interval data that are not normally distributed, which test is appropriate?
A) Kruskal-Wallis H test
B) Friedman test
C) One-way ANOVA
D) Mann-Whitney U test
5. What is the primary purpose of using a power analysis before conducting a study?
A) To ensure the results are statistically significant
B) To determine the minimum sample size required to detect an effect of a certain magnitude
C) To calculate the effect size of the expected outcome
D) To decide whether to use parametric or non-parametric tests
6. Which of the following is a measure of central tendency that is NOT sensitive to outliers?
A) Mean
B) Median
C) Standard Deviation
D) Variance
7. The standard error of the mean (SEM) is a measure of:
A) The variability of individual scores
B) The variability of sample means around the population mean
C) The difference between the mean and the median
D) The spread of the middle 50% of data
8. A researcher finds a correlation coefficient (r) of -0.75. This indicates:
A) A weak positive linear relationship
B) A strong negative linear relationship
C) A weak negative linear relationship
D) No linear relationship
9. Which type of statistical test is used to examine relationships between categorical variables?
A) T-test
B) ANOVA
C) Chi-square test
D) Correlation
10. If a researcher sets an alpha level of 0.05, they are willing to accept a:
A) 5% chance of a Type II error
B) 5% chance of a Type I error
C) 95% chance of a Type I error
D) 95% chance of a Type II error
11. What does a p-value represent in hypothesis testing?
A) The probability of the null hypothesis being true
B) The probability of the alternative hypothesis being true
C) The probability of obtaining the observed results (or more extreme results) if the null hypothesis is true
D) The size of the effect found in the sample
12. A researcher wants to compare the average scores of three different teaching methods. The scores are not normally distributed. Which test should they consider?
A) Independent samples t-test
B) One-way ANOVA
C) Kruskal-Wallis H test
D) Paired samples t-test
13. When dealing with ordinal data, which measure of central tendency is generally preferred over the mean?
A) Mode
B) Median
C) Mid-range
D) Geometric mean
14. Which statistical concept refers to the extent to which a measurement tool measures what it is intended to measure?
A) Reliability
B) Validity
C) Precision
D) Accuracy
15. Which statistical concept describes the reliability or consistency of a measurement tool?
A) Validity
B) Reliability
C) Standardization
D) Central tendency
16. In the context of hypothesis testing, a statistically significant result means that the observed data are:
A) Practically important
B) Unlikely to have occurred by chance alone if the null hypothesis were true
C) Always generalizable to the population
D) Indicative of a large effect size
17. Which of the following is NOT a factor that influences statistical power?
A) Alpha level (significance level)
B) Sample size
C) Effect size
D) The median of the distribution
18. Cohen's d is a common measure of effect size used for comparing two means. A Cohen's d of 0.8 is generally considered:
A) Small effect size
B) Medium effect size
C) Large effect size
D) No effect size
19. Effect size measures the magnitude of a phenomenon or the strength of a relationship between variables. It is independent of:
A) Sample size
B) Statistical significance
C) The direction of the effect
D) The type of statistical test used
20. A Type II error occurs when:
A) A true null hypothesis is rejected
B) A false null hypothesis is rejected
C) A true null hypothesis is retained
D) A false null hypothesis is retained
21. A Type I error occurs when:
A) A true null hypothesis is rejected
B) A false null hypothesis is rejected
C) A true null hypothesis is retained
D) A false null hypothesis is retained
22. Power analysis is used to determine the sample size needed to detect a statistically significant effect of a given size. What is 'power' in this context?
A) The probability of making a Type I error
B) The probability of making a Type II error
C) The probability of correctly rejecting a false null hypothesis
D) The probability of incorrectly retaining a false null hypothesis
23. Which of the following tests is used to analyze ordinal data in a repeated-measures design with three or more conditions?
A) Kruskal-Wallis H test
B) Mann-Whitney U test
C) Friedman test
D) Wilcoxon signed-rank test
24. The Friedman test is a non-parametric test used for comparing three or more related (dependent) groups. It is the non-parametric equivalent of:
A) Independent samples t-test
B) One-way ANOVA
C) Repeated measures ANOVA
D) Paired samples t-test
25. Which non-parametric test is the equivalent of the one-way ANOVA?
A) Mann-Whitney U test
B) Kruskal-Wallis H test
C) Wilcoxon signed-rank test
D) Chi-square test
26. The Kruskal-Wallis H test is a non-parametric test used to compare the medians of how many independent groups?
A) Two
B) Three
C) Three or more
D) Only one
27. The Mann-Whitney U test is the non-parametric equivalent of which parametric test?
A) Paired samples t-test
B) Independent samples t-test
C) One-way ANOVA
D) Repeated measures ANOVA
28. Which non-parametric test is used to compare two independent groups when the dependent variable is ordinal?
A) Wilcoxon signed-rank test
B) Mann-Whitney U test
C) Kruskal-Wallis test
D) Friedman test
29. The Wilcoxon signed-rank test is a non-parametric alternative to the:
A) Independent samples t-test
B) One-way ANOVA
C) Paired samples t-test
D) Chi-square test
30. The sign test is a non-parametric test used to analyze paired data. It relies on the direction (sign) of the difference rather than the magnitude. This test is most appropriate for:
A) Comparing means of independent groups
B) Comparing medians of independent groups
C) Comparing medians of related groups
D) Comparing variances of independent groups
31. Non-parametric tests are used when the assumptions of parametric tests, such as normality, are violated. What type of data are they typically used with?
A) Interval or ratio data
B) Nominal or ordinal data
C) Continuous data
D) Normally distributed data
32. The paired samples t-test is used when the observations are:
A) Independent
B) Related or matched
C) Categorical
D) Nominal
33. A t-test is used to determine if there is a statistically significant difference between:
A) The means of two or more groups
B) The variances of two groups
C) The medians of two groups
D) The modes of two groups
34. Which of the following is a parametric test used to compare the means of two independent groups?
A) Mann-Whitney U test
B) Chi-square test
C) Independent samples t-test
D) Paired samples t-test
35. Parametric tests assume that the data are drawn from a population that follows a specific distribution, typically the:
A) Uniform distribution
B) Normal distribution
C) Exponential distribution
D) Poisson distribution
36. A Z-score represents the number of standard deviations a raw score is from the mean. A Z-score of 0 indicates:
A) A score far above the mean
B) A score far below the mean
C) A score exactly at the mean
D) A score at the maximum possible value
37. In a normal distribution, approximately what percentage of scores fall within three standard deviations of the mean?
A) 68%
B) 95%
C) 99.7%
D) 80%
38. In a normal distribution, approximately what percentage of scores fall within two standard deviations of the mean?
A) 68%
B) 95%
C) 99.7%
D) 75%
39. In a normal distribution, approximately what percentage of scores fall within one standard deviation of the mean?
A) 68%
B) 95%
C) 99.7%
D) 50%
40. The normal curve is also known as the:
A) J-shaped curve
B) U-shaped curve
C) Bell-shaped curve
D) Rectangular curve
41. The Interquartile Range (IQR) is the difference between the third quartile (Q3) and the first quartile (Q1). What does it represent?
A) The total spread of the data
B) The spread of the lowest 25% of data
C) The spread of the middle 50% of data
D) The average deviation from the median
42. The standard deviation is the square root of the variance. What does it represent?
A) The spread of the middle 50% of data
B) The difference between the highest and lowest scores
C) The typical deviation of scores from the mean
D) The most frequent score
43. The variance is calculated as the average of the squared deviations from the mean. What is its unit of measurement?
A) The same as the original data
B) The square of the original data's unit
C) Square root of the original data's unit
D) Unitless
44. Which measure of dispersion represents the average deviation of scores from the mean?
A) Range
B) Variance
C) Standard Deviation
D) Interquartile Range
45. A skewed distribution where the tail is longer on the right side is called:
A) Positively skewed
B) Negatively skewed
C) Symmetrical
D) Bimodal
46. In a perfectly symmetrical distribution, which of the following is true?
A) Mean > Median > Mode
B) Mean < Median < Mode
C) Mean = Median = Mode
D) Mean = Mode < Median
47. Which measure of central tendency is the most frequently occurring score in a dataset?
A) Mean
B) Median
C) Mode
D) Range
48. The median is the score that divides a distribution into two equal halves. What is its percentile rank?
A) 25th
B) 50th
C) 75th
D) 100th
49. Which measure of central tendency is most affected by extreme scores (outliers)?
A) Median
B) Mode
C) Mean
D) Mid-range
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