CHAPTER 10: TWO-SAMPLE TESTS WITH NUMERICAL DATA 1. The t test for the difference between the means of 2 independent populations assumes that the respective a) sample sizes are equal. b) sample variances are equal. c) populations are approximately normal. d) all of the above ANSWER: c TYPE: MC DIFFICULTY: Moderate KEYWORDS: pooled-variance t test, assumption 2. The t test for the mean difference between 2 related populations assumes that the respective a) population sizes are equal. b) sample variances are equal. c) populations are approximately normal or sample sizes are large enough. d) all of the above ANSWER: c …show more content…
b) 7 and 9. c) 18. d) 16. ANSWER: b TYPE: MC DIFFICULTY: Easy KEYWORDS: F test for equality of variances, degrees of freedom 13. The statistical distribution used for testing the difference between two population variances is the ___ distribution. a) t b) standardized normal c) binomial d) F ANSWER: d TYPE: MC DIFFICULTY: Easy KEYWORDS: F test for equality of variances, degrees of freedom 14. The test for the equality of two population variances is based on a) the difference between the 2 sample variances. b) the ratio of the 2 sample variances. c) the difference between the 2 population variances. d) the difference between the sample variances divided by the difference between the sample means. ANSWER: b TYPE: MC DIFFICULTY: Easy KEYWORDS: F test for equality of variances 15. To use the Wilcoxon rank sum test as a test for location, we must assume that a) the obtained data are either ranks or numerical measurements both within and between the 2 samples. b) both samples are randomly and independently drawn from their respective populations. c) both underlying populations from which the samples were drawn are equivalent in shape and dispersion. d) all of the above ANSWER: d TYPE: MC DIFFICULTY:
We conduct an independent sample t-test using Excel, and obtain the following output (see t-test-height)
5. Give the standard deviation for the mean and median column. Compare these and be sure to identify which has the least variability?
1. The researchers analyzed the data they collected as though it were at what level of measurement?- The correct answer is Interval/ratio.
Research results tell us information about data that has been collected. Within the data results, the author states the results are statistically significant, meaning that there is a relationship within either a positive and negative correlation. The M (Mean) of the data tells the average value of the results. The (SD) Standard Deviation is the variability of a set of data around the mean value in a distribution (Rosnow & Rosenthal, 2013).
5. Give the standard deviation for the mean and median column. Compare these and be sure to identify which has the least variability?
e. Now for the same data, Test the hypothesis that the median value of the difference in weights before and after the dieting programme is non-existent. What is the name of this test? Also state what the symmetric CI for the median of the difference would be.
If the total sample size is under 15, two sample t tests are safe if the data shows
Since Dr. Williams does not know the population standard deviation for all his Intro Psych. classes combined, he should use a t-test. Specifically, he should use the t-test for two independent means. The reason he should use this test is because the data uses interval/ ratio scores, there are two independent samples being compared as the experiment utilized a between subjects design, and it is assumed that the data is normally distributed. Also, Dr. Williams is comparing the two classes to each other, not both classes to the population. If he were comparing both classes as a whole sample to the entire population of Intro. Psych students, then it would be better to use a single sample t-test.
One-sample t-test are used in the parametric test which analyzes the means of populations. The t-test for independent groups are statistics that relates difference between treatment means to the amount of variability expected between any two samples of data within the same population (Hansen & Myers, 2012). Critical values are used in significant testing provide a range of t distribution that is used in whether a null hypothesis is rejected. Based on the data below as the level of significance is at .05, thus the critical values would fall under ±1.860 and the t value for this is 1.871 would suggest for the null to be rejected as it is greater than the critical value (Privitera, 2015, p. 267). Based on the population mean of 70 there was a mean difference of
1. Identify each of the unknown samples(use specific data to justify your answers for A and B).
Fry Brothers heating and Air Conditioning, Inc. employs Larry Clark and George Murnen to make service calls to repair furnaces and air conditioning units in homes. Tom Fry, the owner, would like to know whether there is a difference in the mean number of service calls they make per day. Assume the population standard deviation for Larry Clark is 1.05 calls per day and 1.23 calls per day for George Murnen. A random sample of 40 days last year showed that Larry Clark made an average of
We conduct an independent sample t-test using Excel, and obtain the following output (see sheet T-TEST)
Conclusion : Reject the null hypothesis. The sample provide enough evidence to support the claim that mean is significantly different from 12 .
1. Discuss when it is appropriate to use the paired t-test and the Wilcoxon matched-pairs
Assumption 3 is homogeneity of variance, that the variances of the outcome variable in both groups, the male group and the female group, will be equal. The Levene Test for Equality of Variances has a sig. value of .566. This number is higher than .05 and, therefore, implies that the variability of the two groups is about equal.