Exam 1 Review Problems KEY The length of this practice does not reflect the length of the exam The problems below are to provide you with practice for exam Multiple Choice 1 Undercoverage occurs when the sampling frame a matches the population of interest b does not match the population of interest c matches the sample of interest d does not match the sample of interest 2 Adding 10 to every data point will a not increase the standard deviation but will increase the mean b increase the standard deviation but will not increase the mean c will increase both the mean and standard deviation d will not increase either the mean or standard deviation 3 The box in a boxplot is always one standard deviation wide indicates the start and end of the middle 50 of the data is always 2 standard deviations wide a b c d describes the minimum and maximum values from the data 4 A normal distribution is a Skewed right b Symmetric c Skewed left d Centered at 0 5 The state legislature of Kansas is interested in finding out about the opinion of registered voters throughout the state The legislative staff has created a plan to randomly select voters from throughout the state The staff combined the voter registration lists from all the counties in the state to get a single list of all registered voters Using the list of all voters in the state the staff divided the list into rural and urban voters The staff then used a random number generator to select 500 rural and 500 urban voters This sample would best be described as a A simple random sample of 500 registered voters b A simple random sample of 1000 registered voters c A cluster sample of registered voters using counties as clusters d A stratified sample of registered voters using rural urban as strata 6 As part of a class project a college student wanted to estimate the proportion of students at his college that owned a red car To estimate this proportion he went to a large student parking lot during the middle of a class day He found that 325 out of 1037 cars 31 were red What type of sampling method was used here a A volunteer response sample b A stratified random sample with color of car as the strata c A simple random sample d A convenience sample 7 Given that a variable X is normally distributed with mean and standard deviation why might we convert to a z score a to find the distribution of X b to easily compare it to other observations c d to determine the mean and variance of the distribution to tell whether the data is skewed 8 Suppose we want to know the average age of all students taking ST 311 this semester We take a random sample of 15 students and get a sample mean of 21 4 What is the parameter of interest a the average age of the 15 students measured b the sample mean of 21 4 c d the average age of all students taking ST 311 during this semester the average age of all students who have ever taken ST 311 at NCSU 9 The histogram below gives information about the number of credits taken by a sample of students Which statement is correct about this histogram a The histogram is skewed left so the sample mean is less than the sample median b The histogram is skewed left so the sample mean is greater than the sample median c The histogram is skewed right so the sample mean is less than the sample median d The histogram is skewed right so the sample mean is greater than the sample median 10 A pharmaceutical company did research on candidates for a drug trial They recorded each patients weight in lbs blood pressure in mmHgs race White Black Asian Other zip code 27511 or 27606 and level of breathing difficulty None Some or Extreme Which of the following is true about the variables recorded a Race and zip code are the only categorical variables b Race zip code and level of breathing difficulty are the only categorical variables c Race and level of breathing difficulty are the only categorical variables d Zip code and level of breathing difficulty are the only categorical variables 11 Consider the two distributions below What is true about the standard deviation of the distributions a Distribution A has a smaller standard deviation than distribution B b Distribution B has a smaller standard deviation than distribution A c The standard deviations of the two distributions are approximately the same d There is not enough information given to answer the question 12 In a simple random sample the problem of non response bias occurs when a The sampling frame does not contain all individuals in the population b Some individuals that are randomly selected refuse to participate c Some individuals who answer the questions do not answer the question truthfully d Both B and C but not A 13 A certain firm has 500 employees An auditor wishes to estimate the average number of days of sick leave taken per employee over the past quarter The firm has eight divisions with varying numbers of employees per division The auditor decides to randomly sample 3 divisions and finds the number of sick days each employee within these divisions take This sample is best described as a A stratified sample using the divisions as strata b A cluster sample using the divisions as clusters c A simple random sample of 500 employees d A simple random sample of an unknown number of employees Use the information below for questions 14 through 16 A local corporation was interested in the purchasing habits of Wake County residents One of the things they were interested in was the proportion of residents that did a major home improvement project in the last year The corporation used a list of all households in the county to take a simple random sample The researcher then visited each of the sampled homes and found that 21 of 100 homes had completed a major home improvement project 14 What is the population of interest in this situation a All Americans b All Wake County residents c All Wake County residents who have completed a major home improvement project in 15 What is the parameter of interest in this situation a The proportion of all Wake County residents who did a major home improvement the last year d The 100 homes that were sampled project in the last year b 21 c The 100 homes that were sampled d All Wake County residents 16 What is the sampling frame in this situation a The 100 homes that were sampled b Major home improvement projects c The local corporation that conducted the sample d The list of all households in the county 17 A local politician is interested in the public opinion