Reading Application #8

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435

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Apr 3, 2024

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EPSY 435 Educational Statistics Reading Application #8 (Chapters 11 and 12) Choose the correct answer from the choices provided. - You can type your answers by indicating A, B, C, or D. Please provide reasons for each of your answers. 1. If your degrees of freedom is 99, your sample size when conducting a t -test for dependent means must be _______. D) 100 This answer is correct because when calculating the degrees of freedom, it is n-1. So, to find the sample size, all you need to do is reverse the equation 99+1, which is 100. So, the sample size is 100. 2. If the obtained value is greater than the critical value, what should you do? A) Reject the null hypothesis This answer choice is correct because when the obtained value is greater than the critical value, that means the p-value is less than the alpha. This means that there is more evidence against the null therefore, you reject the null. 3. The t -test for dependent means is used when your sample is tested _______. B) more than once This answer choice is correct because in order for you to use the t-test for dependent means, there has to be two related groups that are tested more than once. Like a pretest and posttest in school. If they are two different groups, then it would be a t-test for independent means. 4. In order to be 99% confident you have not committed a Type I error, at what level should you set your p -value? A) .01 This answer choice is correct because if you set your p-value at .01 then you are giving yourself the smallest chance of making an error because .01 is what remains when subtracting 99% from 100%. The p-value is the probability value, so the more confident I am, the less my p-value has to be. For example, if I am 95% confident my p-value will be set at .05 or if I have the p-value of .04 my confidence level would be 96%. 5. In order to determine whether or not you will reject the null hypothesis, the test statistic must be compared against the____. A) critical value This answer choice is correct because in order to reject the null the obtained value (test statistic) has to be compared to the critical value. The critical value
shows us the rejection region and if the obtained value is in the rejection region then the null is rejected. Therefore, the critical value is needed to determine whether or not you will reject the null hypothesis. Look at the following scenarios and decide what kind of t -tests should be used. Please provide reasons for your answers. Your reasons must reflect the information in that particular scenario. 6. Gary wants to know whether the mean petal length of iris flowers differs according to their species. He finds two different species of irises growing in a garden and measures 25 petals of each species. What type of t -test should he use and why? b) T -test for independent samples Gary should use the t-test for independent samples because he is examining the petal length of two different species of irises. Because he is examining two different species of irises, he should use the t-test for independent samples. 7. A researcher conducts an experiment to see if specific eye exercises can improve peripheral vision. A random sample of 5 people were rated for peripheral vision on a scale from 1 to 20 where 9 is considered average and higher scores indicate better peripheral vision. Then they followed the prescribed eye exercise program and were tested again. What type of t -test should be used and why? a) T -test for dependent samples The researcher should use the t-test for dependent samples because they are examining if specific eye exercises can improve peripheral vision in a random sample of 5 people. The people were tested and then tested again after they followed the prescribed eye exercise program. Because it was the same group given a pre-test and a post-test, the researcher should use the t-test for dependent samples. 8. Dr. Ramos plans on giving the EPSY 435 students a diagnostic test before teaching the topic on linear regression and then another test after teaching the topic to see if the students’ knowledge of linear regression has increased. What type of t -test should she use and why? a) T -test for dependent samples Dr. Ramos should use the t-test for dependent samples because she is testing to see if the student's knowledge of linear regression has increased after teaching the topic. Because she is
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