You are conducting a study to see if students do better when they study all at once or in intervals. One group of 12 participants took a test after studying for one hour continuously. The other group of 12 participants took a test after studying for three twenty minute sessions. The first group had a mean score of75 and a variance of 120. The second group had a mean score of 86 and a variance of 100. a. What is the calculated t value? Are the mean test scores of these two groups significantly different at the .05 level? b. What would the t value be if there were only 6 participants in each group? Would the scores be significant at the .05 level? Solution A) Formulating the null and alternative hypotheses, Ho: u1 - u2 = 0 Ha: u1 - u2 =/ 0 At level of significance = 0.05 As we can see, this is a two tailed test. Calculating the means of each group, X1 = 75 X2 = 86 Calculating the standard deviations of each group, s1 = 10.95445115 s2 = 10 Thus, the standard error of their difference is, by using sD = sqrt(s1^2/n1 + s2^2/n2): n1 = sample size of group 1 = 12 n2 = sample size of group 2 = 12 Thus, df = n1 + n2 - 2 = 22 Also, sD = 4.281744193 Thus, the t statistic will be t = [X1 - X2 - uD]/sD = -2.569046516 [ANSWER, T VALUE] ******************************** b) Calculating the means of each group, X1 = 75 X2 = 86 Calculating the standard deviations of each group, s1 = 10.95445115 s2 = 10 Thus, the standard error of their difference is, by using sD = sqrt(s1^2/n1 + s2^2/n2): n1 = sample size of group 1 = 6 n2 = sample size of group 2 = 6 Also, sD = 6.055300708 Thus, the t statistic will be t = [X1 - X2 - uD]/sD = -1.816590212 [ANSWER] For part A, the P value is p = 0.01750305 For part B, the P value is p = 0.099328388 Hence, Part A would be significant, but part B wouldn\'t. [ANSWER] ********************************** ***************************************************** Hi! If you use another method/formula in calculating the degrees of freedom in this t-test, please resubmit this question together with the formula/method you use in determining the degrees of freedom. That way we can continue helping you! Thanks! ********************************************.

1. You are in charge of the investigation regarding possible exposure to Listeria from packaged
salad. Read the following and hen answer the questions: On January 27, Dole voluntarily
recalled all salad mixes produced in the Springfield, Ohio processing facility. A list of the
recalled brands and types of salad mixes, states where they were sold, and instructions on how to
identify them are available on the Advice to consumers page. Three more ill people have been
reported from Connecticut, Missouri, and New York. The most recent illness was diagnosed on
January 3, 2016. According to the Public Health Agency nada, there are seven people in five
Canadian provinces infected with the same outbreak strain of Listeria. First of all, complete the
epidemiological triangle for this exposure Can t be Listeria? Explain. Second, Develop a specific
case definition for this exposure and then clearly state how you would define a Confirmed case,
Probable case, Possible Case and Suspect case. Lastly, how would you gather information
regarding the number and location of cases associated with this exposure?
Solution
a.
Listeriosis is a type of food poisoning, caused by the gram-positive motile bacterium
Listeriamonocytogenes. Listeriosis is relatively rare and occurs primarily in new born infants,
elderly patients, and patients who are immunocompromised. Symptoms of listeriosis may show
up 2-30 days after exposure. Symptoms are mild flu-like headaches, muscle aches, fever, nausea,
and vomiting. If the infection spreads to the nervous system it can cause stiff neck,
disorientation, or convulsions.
Epidemiologic and laboratory evidence indicated that packaged salads produced at the Dole
processing facility in Springfield, Ohio and sold under various brand names were the likely
source of this outbreak.