Question 1
Given a sample with 5 scores: 4, 6, 8, 10, and y, and the mean of this sample is 6, what is the variance of the sample? (Hint: first find y). 10
Answer
1 points (Extra Credit)
Question 2
Given a population mean weight of 150 pounds and a population standard deviation 40 pounds, express an individual weight of 200 pounds as a z-score. (to two decimal places, e.g.: 3.21 or 6.00) 1.25
Answer
1 points (Extra Credit)
Question 3
Find the correlation coefficient for these scores (they are given in the form (x1,y1), (x2,y2) etc): (0,1), (10,3), (4,1), (8,2), (8,3) (express this to 3 decimal places, e.g.: .123 or -.456) 0.875
Answer
1 points (Extra Credit)
Question 4
Use the least squares regression equation to find the predicted Y value for an X value of 5, given: r = .3, SSy=64 , SSx=4 , mean of y= 30, mean of x= 10 24
Answer
1 points (Extra Credit)
Question 5
You're going skydiving, because you're awesome. The main parachute has to do two things to keep you alive: release when you pull the cord, (probability of releasing = .9) AND unfold properly (probability of unfolding = .8). Unfolding is independent of releasing. OR, if anything goes wrong, your backup parachute will save you (probability of backup working = .7). The backup parachute only comes into play if the first parachute fails. What is the probability that you survive, i.e. that either your primary OR secondary parachute will work? (Hint: this combines both independent and mutually exclusive events, and the answer will be greater than .9). Give the answer to three decimal places, e.g.: .999 0.986
Answer
1 points (Extra Credit)
Question 6
Does eating vegetables instead of delicious foods affect how long you live? Given a population life expectancy of 75 years with population standard deviation 5 years, What is the z-value for a random sample of 25 vegans who live to an average age of 73? Does this alter life expectancy at a .05 level of significance? Type the z-value in box 1 to two decimal places (e.g. 3.45), and in box 2 type either yes or no (yes if this is statistically significant and you reject the null, no if it is not significant and you fail to reject the null). -2.00 Yes
Answer
1 points (Extra Credit)
Question 7
A similar follow-up study is done on a sample of 25 meat-lovers who never eat vegetables, again randomly selected from the same general population (population mean life expectancy = 75, population standard deviation = 5). This new sample of meat-eaters live to an average age of 77. What is the lower limit and upper limit of the 95% confidence interval for the life expectancy of this sample of meat-lovers? Type the lower limit in box 1 and the upper limit in box 2, to two decimal places in each case. 75.04 78.96
Answer
1 points (Extra Credit)
Question 8
Is working out every day BETTER than working out every other day but for twice as long? A random sample of 42 people are assigned to two groups of equal size: Group 1 works out every day for one hour, Group 2 works out every other day for two hours, and then after a month they are tested for how many pushups they can do in one minute. Group 1 participants do an average of 43 pushups, Group 2 participants do an average of 32 pushups. Given an estimated standard error of 6 pushups, what is the t-value? Is the Group 1 workout plan statistically significantly BETTER than the Group 2 workout plan, at the .05 level? Give the calculated t-value to two decimal places in box 1, and in box 2 type either yes (if it is statistically significant and you reject the null) or no if it is not significant. 1.83 Yes
Answer
1 points (Extra Credit)
Question 9
Does study group size affect test performance? From a large class of students, 12 are selected to study for a test either all alone, with a partner, or with a group of other students. The four students who studied alone scored: 7, 10, 9, and 6; the four students who studied with a partner scored: 8, 8, 9, and 7; and the four students who studied in groups scored: 7, 6, 4, and 3. What is the F-value for this study (type in box 1 to two decimal places), and is there a statistically significant effect of study group size on test performance at the .05 level, based on this data (type yes or no in box 2)? 4.91 Yes
Answer
1 points (Extra Credit)
Question 10
Do blondes have more fun? Walking around downtown Saturday night, you ask people whether they had a boring time, a good time, or a great time that night, and note their hair color. Out of 80 blondes: 20 had a boring night, 20 had a good night, and 40 had a great night. out of 120 non-blondes: 30 had a boring night, 40 had a good night, and 50 had a great night. What is the chi-square value for this data (type in box 1 to two decimal places) and is there statistically significant relationship between hair color and fun at the .05 level (type yes or no in box 2)? 1.85 No