HCD 300 Participation and Homework 9

What is the test statistic? - (-3.13) - 2.30 - 1.69 - 2.06

(-3.13) - use t-test: paired and find t-stat - if lower than p-value, then statistically significant and reject the null hypothesis

What formula correctly calculates the degrees of freedom for equal variance in independent samples? - (n1-1) + (n2-1) - n-1 - 1+n

(n1-1) + (n2-1) - degrees of freedom is used to approximate sample size. n= number of observations and this formula is used for equal variance; degrees of freedom approximate sample size

What is the effect size? - 0.42 - 0.70 - 1.0 - 0.0019

0.70

20 students were observed to see how their scores were affected before and after a module. What are the degrees of freedom in this example? - 19 - 20 - 21

19 (n-1 where n is the number of pairs) - 20 minus 1 = 19

Two departments who are competing in a walking challenge. The average minutes walked each day by the members of each department are listed below. What is the two-tail critical value? - 2.56 - 3.144 - 7.58 - 2.144

2.144 (Use Excel Analysis Tookpak - Choose T-test: two-sample assuming unequal variances)

What is the test statistic? - 0.89 - 0.57 - 2.32 - 2.79

2.32

What is the degrees of freedom for this study? - 50 - 23 - 24 - 1

24 (25-1 = n-1)

Two departments are competing in a walking challenge. The average minutes walked each day by the members of each department are listed below. What is the test statistic? Group 1: 17, 22, 5, 15, 12, 20, 14, 15, 20, 21 Group 2: 6, 9, 12, 11, 11, 8, 13, 14, 7 - 1.5 - 5.62 - 3.211

3.211 - test statistic can be found in Excel using T.TEST function or using analysis Toolpak "t-test: two-sample assuming unequal variances" - include a 3 at the end of the T.TEST to ensure unequal variances being assumed OR use the T-Test Assuming Unequal Variances

What is the degrees of freedom for this study? - 43 - 42 - 22 - 21

42 - (n1-1) + (n2-1) -> (22-1) + (22-1)

What type of test would be used to evaluate the performance of 10 individuals in a spelling bee if they were observed before AND after they took a course to improve their spelling? - A two-sample t-test with independent samples - A z-test - A two-sample t-test with dependent samples

A two-sample t-test with dependent samples

Which of the following is a limitation to using a two-sample t-test for dependent samples? - Assumption of equal variances - The assumption that sample size is never equal - Results of study can only be compared to other studies

Assumption of equal variances

For two-sample t-tests, results cannot be compared between studies. The test statistic is given, as well as a p-value. This test is also known as a matched sample or paired t-test. - The location of the population - Affected by time of day - Assumption of normal distribution

Assumption of normal distribution

What is the assumption for equal variance? OR How do you determine equal or unequal variance? - Calculate the ratio of the sample variances. The ratio should be between 0.5 and 2. - Calculate the ratio of the sample variances. The ratio should be between between 1 and 3. - The sample sizes have nothing to do with the variance. - Calculate the ratio of the sample variances. The ratio should be between between 5 and 10.

Calculate the ratio of the sample variances. The ratio should be between 0.5 and 2.

What is the assumption for equal variance? OR How do you determine equal or unequal variance? - Calculate the ratio of the sample variances. The ratio should be between between 1 and 3. - The sample sizes have nothing to do with the variance. - Calculate the ratio of the sample variances. The ratio should be between between 5 and 10. - Calculate the ratio of the sample variances. The ratio should be between 0.5 and 2.

Calculate the ratio of the sample variances. The ratio should be between 0.5 and 2.

What is the appropriate measure of effect for a two-sample test? - Correlation - none of the above - Cramer's V - Cohen's d

Cohen's d (for dependent and independent)

What is the effect size of a cohen's d value of .80? - Small - Large - Medium

Large

How would you interpret this effect size? - Medium - Strong - Weak

Medium

What is the criteria for a two-sample z-test? - Sample size under 30, population standard deviation is known - Sample size over 30, population standard deviation is known - Sample size under 30, population standard deviation is unknown - Population standard deviation unknown, sample size over 30

Sample size over 30, population standard deviation is known

What is the criteria for a two-sample t-test with dependent samples? - The sample sizes should be unequal - Sample size should be equal - The ratio of the variances of each group should be less than 3

Sample size should be equal

What is the criteria for a two-sample t-test with dependent samples? - Sample size should be equal - The ratio of the variances of each group should be less than 3 - The sample sizes should be unequal

Sample size should be equal (Two-sample t-tests with dependent samples are called matched sample or paired t-test; comparing the means, which must be matched)

What is the criteria for a two-sample t-test? - Sample size over 30, population standard deviation is known - Population standard deviation unknown, sample size over 30 - Sample size under 30, population standard deviation is unknown

Sample size under 30, population standard deviation is unknown

What is the effect size of a Cohen's d value of 0.2? - Small - Medium - Large

Small

What is the Excel function for a two-sample t-test with dependent samples? - TTEST - TWOSAMPLE - TVAL - ZTEST

TTEST

Which of the following is a limitation to using two-sample t-tests with independent samples? - They are affected by the timing of the sample - They are affected by the demographic of the sample - They are affected by sample size

They are affected by sample size (Results of analyses from different studies can not be compared)

True or False, this finding is statistically significant. - True - False

True

True or False, this finding is statistically significant. - true - false

True (P-value = 0.0045 and t statistic was -3.13)

Two departments are competing in a walking challenge. The average minutes walked each day by the members of each department are listed below. Determine equal or unequal variances? Group 1: 17, 22, 5, 15, 12, 20, 14, 15, 20, 21 Group 2: 6, 9, 12, 11, 11, 8, 13, 14, 7 - Unequal - There is not enough information provided to determine the variances. - Equal

Unequal

Which of the following is a limitation to two-sample t-tests with independent samples? - You can only evaluate two sample t-test with equal variances - You can only evaluate the means - You cannot evaluate anything

You can only evaluate the means

Set the level of risk (or the level of significance or Type I error) associated with the null hypothesis. The level of risk or Type I error or level of significance. Any other names for this value? (Salkind, p. 244) - test statistic - p-score - critical value - alpha

alpha

What is the effect size of a Cohen's d value of 0.50? - small - large - medium

medium

What is the correct formula for the degrees of freedom for a two-sample t-test with dependent samples? - n + 2 - n - 1 (where n is the number of total observations) - n-1 (where n is the number of pairs - (n1-1) + (n2-1)

n-1 (where n is the number of pairs)

Based on this information, the researcher should make the decision to ___________. - reject the null hypothesis - fail to reject the null hypothesis

reject the null hypothesis

Researchers want to test the effectiveness of a new drug at treating hypertension. They have 100 participants who are divided into two groups. Group 1 receives a standard hypertension drug and Group 2 receives the new medication. After one month the blood pressure readings of each group are measured. What is the appropriate test to use? - two sample t-test for independent samples - one-sample z-test - two-sample t-test for dependent samples - none of the above

two sample t-test for independent samples (Blood pressure results aren't dependent on anything so it's independent)

A group of 25 people were asked to remember as many items as possible from a list before and after being taught a memory device. Researchers choose α = 0.05 level to test their results. For your convenience, I have prepared an excel file with this information titled: Data_biostats homework_two sample_memory. Use this data to answer questions 4-9. A group of 25 people were asked to remember as many items as possible from a list before and after being taught a memory device. Researchers choose α = 0.05 level to test their results. Group 1: 3, 5, 4, 5, 5, 5, 4, 5, 5, 8, 7, 7, 7, 6, 7, 8, 7, 9, 5, 6, 7, 7, 6, 8, 8 Group 2: 5, 6, 5, 5, 7, 8, 5, 6, 6, 8, 8, 7, 8, 6, 8, 9, 6, 8, 5, 6, 7, 6, 7, 8, 9 What is the proper test to use? - two-sample t-test for independent samples - two-sample t-test for dependent samples - none of the above - one-sample z-test

two-sample t-test for dependent samples

You have a sample of 45 3rd graders who took a reading comprehension test before and after participating in a reading program. The scores on the reading comprehension test are then compared. What is the appropriate test to use? - two-sample t-test for dependent samples - none of the above - two-sample t-test for independent samples - one-sample z-test

two-sample t-test for dependent samples (45 3rd graders sample of reading comprehension test BEFORE AND AFTER participating in reading program -> dependent)

A group of 44 women with gestational diabetes were assigned to one of two groups. Group 1 received standard care, and group 2 participated in group counseling visits. Researchers want to determine whether or not the birthweights of the infants of the mothers who participated in the group counseling visits were significantly different than the birth weights of mothers who received standard care at the α = 0.05 level. For your convenience, I have prepared an excel file with the birth weight in grams for both groups below. Use this data to answer questions 10-15. Group 1: 4350, 4225, 4650, 5400, 3850, 4450, 4375, 3950, 4525, 5200, 4800, 4275, 4175, 4230, 4650, 4300, 4650, 4725, 4325, 4225, 4350, 4585 Group 2: 4395, 4375, 4225, 3335, 3975, 4020, 3725, 3825, 4125, 4425, 4375, 4055, 4500, 4875, 3855, 3955, 4355, 3975, 4550, 4325, 4675, 4745 What is the proper test to use? - two-sample t-test for dependent samples - two-sample t-test for independent samples - none of the above - one-sample z-test

two-sample t-test for independent sample