Practice Test 2

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School

University of British Columbia *

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380

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Statistics

Date

Apr 3, 2024

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docx

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Uploaded by ElderFog6364

Total points: 15 Total time: 20 mins The approximate time each question should take is listed beside each question. Question 1A. (5pts) In the US National Elections Study (2020) dataset there is a variable measuring “feelings toward the NRA”. The unit of analysis is, of course, US citizens. The NRA , National Rifle Association, is an interest group that lobbies against gun control. The histogram below presents the distribution NRA ratings for two groups: A) People who do not own a gun &, B) People who own at least one gun. Label the two histograms with the correct group. In a few sentences, explain your choice. In your answer, describe the distribution of the variable for at least one of the groups. Use some numbers to help readers understand the distribution. Formulas to consult: s = √ ∑ i = 1 n ( Y i − ¯ Y ) 2 n − 1 = sample standard deviation

Q2 (3pts): Write down you real student number. Subtract the number 111,111 from your student number. So, if your student number happened to be 25388899, the new number is 25277788. The digits of the new number are going to be 8 separate ratings of “mayonnaise” (on a 0 to 9 scale). So, each digit is a rating of “mayonnaise” from some randomly sampled Canadian. For the example above, we have the following ratings: 2,5,3,8,8,8,9,9. And the mean of those ratings is 6.5. You will now calculate the mean, standard deviation, and standard error of the mean. This should take about 10 minutes. 1. (1 pt) Report the mean rating of mayonnaise in your sample, rounded to an integer (round numbers). 2. (2 pts) Report the standard deviation of the ratings in your sample. Note: since your values are all integers, and the mean is an integer, you will have integers for your deviations, squared deviations, and the sum of the squared deviations. For the final step (divide by n-1 then take the square root), do not round anything. Your answer should be rounded to one decimal place. Q4A (1pts) Select all of the following statements that are CORRECT about the sampling distribution of the sample mean: A. The mean of the sampling distribution is the same as the true (unknown) population mean. B. The standard error of the sample mean is a measure of the variability of the sample mean among repeated samples. C. The sampling distribution shows how the sample mean will vary among repeated samples. D. The standard error of the sample mean will decrease as the sample size increase E. The sampling distribution shows how the sample was distributed around the sample mean. There will be a few more questions on the basic ideas from Week 6. You should know: -the difference between a population and sample -whether the mean of a sample will vary across different samples - the 68/95/99 rule regarding the normal distribution.

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