Stats final Exam

The time to complete a standardized exam is approximately Normal with a mean of 70 minutes and a standard deviation of 10 minutes. How much time should be given to complete the exam so that 80% of the students will complete the exam in the time given?

78.4 minutes

A public opinion poll in Ohio wants to determine if registered voters in the state approve of a measure to ban smoking in all public areas. They select a simple random sample of fifty registered voters from each county in the state and ask whether they approve or disapprove of the measure. This is an example of a

stratified random sample

Below is a scatter plot (with the least-squares regression line) for calories and protein (in grams) in one cup of 11 varieties of dried beans. The computer output for this regression is below the plot. Lima beans have 621 calories and 37 grams of protein. What is the residual for lima beans?

-4.18

Ignoring twins and other multiple births, assume that babies born at a hospital are independent random events with the probability that a baby is a boy and the probability that a baby is a girl both equal to 0.5. What is the probability that the next five babies are girls?

0.03125

The two-way table below gives information on the performers in the New York Philharmonic Orchestra, categorized by section (type of instrument) and gender. You select one musician from this group at random. What is the probability that this person plays a woodwind?

0.159

DeAnna's school bus arrives at her stop at 6:00 am. If she misses the bus, her father drives her to school. Let event B = DeAnna catches the bus and F = DeAnna makes it to her first period class on time. The tree diagram summarizes the probabilities in this situation. Given that DeAnna makes it to her first class on time, what is the probability her father drove her to school?

0.168

A review of voter registration records in a small town yielded the following table of the number of males and females registered as Democrat, Republican, or some other affiliation. What proportion of males are registered as Democrats?

0.30

The distribution of household incomes in a small town is strongly skewed to the right. The mean income is $42,000 and the standard deviation is $24,000. The Fornof family's household income is $60,000. What is the z-score for the Fornof family's income?

0.75

A basketball player makes 160 out of 200 free throws. What would we estimate the probability that the player makes his next free throw to be?

0.80

Consider the following scatterplot of the amount of CO (carbon monoxide) and NOX (nitrogen oxide) in grams per mile driven in the exhausts of cars. The least-squares regression line has been drawn in the plot. Based on the scatterplot, the least-squares regression line would predict that a car that emits 10 grams of CO per mile driven would emit approximately how many grams of NOX per mile driven?

1.1

The heights of American men aged 18 to 24 are approximately Normally distributed with a mean of 68 inches and a standard deviation of 2.5 inches. About what percentage of the men are over 70.5 inches tall?

16

You are examining the relationship between x = the height of red oak trees and y = the number of acorns produced in a five-year period. You calculate a correlation coefficient and a least-squares regression line. If you switched the variables (that is, let x = number of acorns and y = height of trees), which of the following would be true?

The correlation coefficient would not change, but the regression line would change.

The following is a histogram showing the actual frequency of the closing prices of a particular stock on the New York Stock Exchange over a 50-day period. Without doing any calculations compare the values of the mean and the median.

The mean is larger than the median because the histogram is skewed to the right.

Below is a histogram of the heights of gold-medal-winning high jumps in the Olympic Games since 1896. Which of the following statements is supported by this histogram?

The median jump is between 80 and 85 inches.

Different writers have different styles. One way to quantify this difference is to compare the distribution of word lengths in their work. Below are parallel boxplots describing the distributions of word lengths for the first 60 words in Henry James's The Turn of the Screw, J.K. Rowling's Harry Potter and the Chamber of Secrets, and Chapter 1 of your statistics textbook (labeled "Starnes"). Based on the graphs, which one of the following statements must be true?

The median word length for Rowling is longer than for either Starnes or James.

A group of 125 pick-up truck owners were asked what brand of truck they owned and whether it had four-wheel drive. The results are given in the two-way table below. You randomly select one truck owner. Which one of the following is true about the events "Owner has a Chevy" and "Owner's truck has four-wheel drive"?

These two events are not mutually exclusive, but they are independent.

You are told that your score on an exam is at the 85th percentile of the distribution of scores. Which of the following is a correct interpretation of this information?

Your score was the same as or greater than approximately 85% of the people who took this exam.

A television station is interested in predicting whether voters in its viewing area are in favor of offshore drilling. It asks its viewers to phone in and indicate whether they support/are in favor of or are opposed to this practice. Of the 2241 viewers who phoned in, 1574 (70%) were opposed to offshore drilling. The viewers who phoned can best be described as

a voluntary response sample.

Mrs. De La Fe, a sportswriter, wants to know how strongly Orlando residents support the professional baseball team, the Orlando Rays. She stands outside the stadium before a game and interviews the first 20 people who enter the stadium. The intended population for this survey is

all residents of Orlando.

A double-blind experiment was conducted to evaluate the effectiveness of the Salk polio vaccine. The purpose of keeping the diagnosing physicians ignorant of the treatment status of the experimental subjects was to

eliminate a possible source of bias.

We wish to draw a sample of 5 without replacement from a population of 50 households. Suppose the households are numbered 01, 02, . . . , 50, and suppose that the relevant line of the random number table is 11362 35692 96237 90842 46843 62719 64049 17823. The households selected are

households 11, 36, 23, 08, and 42

The customer service department of an online store keeps track of the length of time customers wait on hold for a representative. The mean wait time is 5 minutes and the standard deviation is 2.3 minutes. Suppose the company wants to change the variable from minutes to seconds exceeding a target time of 120 seconds. That is, if X is wait time in minutes, the new variable is Y = 60X - 120. Which of the following are the mean and standard deviation of Y?

mean = 180, standard deviation = 138

The height (in feet) and volume (in cubic feet) of usable lumber of 32 cherry trees are measured by a researcher. The goal is to determine if volume of usable lumber can be estimated from the height of a tree.If the data point (65, 70) were removed from this study, how would the value of the correlation r change?

r would be larger, because this point does not fall in the pattern of the rest of the data.

A researcher wishes to determine whether the rate of water flow (in liters per second) over an experimental soil bed can be used to predict the amount of soil washed away (in kilograms). In this study, the explanatory variable is

the rate of water flow.

Mrs. Austin measures the age, marital status and earned income of an SRS of 1463 women. The number and type of variables you have measured is

three; one categorical and two quantitative.