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21. Take the formula Z = (X - )/, where is the mean of the population, X is the value of the element, Z is the z-score and is the standard deviation. What does this formula calculate? A. Confidence interval. B. Standard score. C. Standard error of the mean. D. Variance.

22. A population has a mean of =35 and a standard deviation of =5. After 3 points are added to every score in the population, what are the new values for the mean and standard deviation? A. =35 and =5 B. =35 and =8 C. =38 and =5 D. =38 and =8

23. Of the following Z-score values, which one represents the location closest to the mean? A. Z=+0.5 B. Z=+1,0 C. Z=-1.5 D. Z=-0.3

24. If the scores on a test have a mean of 26 and a standard deviation of 4, what is the z-score for a score of 18? A. 2 B. 11 C. -2 D. -1.41

25. A population has a =50 and =10. If these scores are transformed into z-scores, the population of z-scores will have a mean and standard deviation of: A. =50 and =10 B. =50 and =1,96 C. =1 and =0 D. =0 and =1

26. If all possible samples of size n=30 are selected from a population with =80 and =10 and the mean is computed for each sample, then what shape is expected for the distribution of sample means? A. The sample means tend to form a normal-shaped distribution whether the population is normal or not. B. The sample means tend to form a normal-shaped distribution only if the population distribution is normal. C. The sample size of n=30 is too small to predict the shape of the distribution. D. The mean of each sample will be very close to 80, hence the distribution of means will have little variability.

27. What is a definition of the standard error? A. Standard deviation of the sample. B. Squared standard deviation. C. Standard deviation of sample means. D. Standard deviation of the population mean.

28. If a researcher sets a level of significance at .05 (i.e. 5%), what does this mean? A. Five times out of 100, a significant result will be found that is due to chance alone and not to true relationship. B. Ninety-five times out of 100, a significant result will be found that is due to chance alone and not to true relationship. C. Five times out of 100, a significant result will be found that is not due to chance, but to true relationship. D. None of the above.

29. When does a researcher risk a Type I error? A. Anytime the decision is 'fail to reject'. B. Anytime H0 is rejected. C. Anytime H1 is rejected. D. All of the above options.

30. Which of the following assumptions are required if an independent t-test is to be used? A. Samples are drawn from a normally distributed population. B. Homogeneity of variances (equal variances). C. The data are either interval or ratio scales. D. All the above assumptions (A, B and C) are required.