Partial preview of the text
Download Midterm Exam (Practice Problems) - Introduction to Statistical Methods | STAT 301 and more Exams Data Analysis & Statistical Methods in PDF only on Docsity!
STAT 301 ~ 003 Spring 2010 Practice Problems Sampling Distributions 1. For each of the following scenarios, state whether or not we know the approximate sampling distribution of the statistic and why. If we do know it, provide it (with its mean and variance). a. ‘The Forest Service wants to know the average number of bark beetles residing on each tree ina certain forest. Unbeknownst to the Forest Service, the number on each tree follows a highly skewed distribution with a mean of 37 beetles with a variance of 68. The Forest Service selects 35 trees at random, counts the number of bark beetles on each, and calculates the mean. b. A biologist wants to study the prevalence of a common skin condition in a large population of chimpanzees. The (unknown) population proportion of chimps with the condition is .42. The biologist samples 25 chimpanzees from the population and calculates the proportion that has the skin condition. 2. TAS test scores (unlike the SAT’s) are known to have a non-normal distribution. The test has a mean score of 75 with a variance of 144. A class of 32 students takes the test. a. What is the probability that the average score for the class is higher than 78? b. What is the probability that the average score for the class is less than 797 
