# Statistics 2 Quiz

### 1.

You have data on the incomes of retirees in your community. A sample of 50 looks like this in the graph below. Suppose you took another sample of 50 incomes, found their mean, and plotted it on a number line. Suppose you did this over and over until you had 1000 means from 1000 samples. Approximately what would the shape of the distribution of these 1000 means look like?

### 2.

The context and purpose of a hypothesis test are best described how?

### 3.

You are working in an area where the cost of each measurement is very high so you have to make do with 10 observations. A dot plot looks like the image shown. You were planning to use the t-distribution to construct a confidence interval for the mean but it looks like you have a problem with

### 4.

The graph below is a bootstrap distribution of the mean house value (\$million) in a high-end neighborhood in San Francisco, based on a sample of 10. To find the endpoints of a 90% confidence interval, you would

### 5.

After some research in the library, you find two studies on a subject that interests you – the number of playing days a typical NFL (football) player loses due to injury in his career. One had a sample size of 30 and the other a sample size of 150. For which study would you expect the standard error of the mean to be smaller?

### 6.

You wanted to test the hypothesis that a population parameter is zero. You asked your assistant to do the analysis. They did everything correctly except they generated a confidence interval instead of a hypothesis test. The confidence interval ranges from -23 to -15. What is your conclusion?

### 7.

You wish to do a study to measure a relatively small effect. Increasing the sample size will

### 8.

If the probability that mortgage A defaults is 0.1, and the probability that mortgage B defaults is 0.2, what is the probability that both will pay off on time? What assumption is required for this answer to be strictly accurate?

### 9.

You have sample data on two groups as follows: You want to estimate the population mean for each group. For which group will the estimate be more precise?

### 10.

If you increase the sample size in a survey, what will normally happen to the power of a statistical test on the data?

### 11.

What is the difference between "standard deviation" and "standard error"?

### 12.

A website administrator is worried about response times for a web page to load, the target is an average of 2 seconds. A test is run at a variety of times, and the following results are obtained (secs): 0.8, 0.9, 1.9, 3.2, 4.0, 0.7, 1.2, 5.6, 3.9, 2.7. You have been asked to do a very quick analysis to summarize this data. You take 1000 bootstrap samples and plot a distribution of these resample means (see figure). What would your report most likely look like?

### 13.

A health services provider has grown and now wants to use patient data to modify its procedures to produce better patient outcomes. Typically, 15% of patients seen for respiratory problems come back to the doctor within 10 days. The provider wants to try a new procedure in which the doctor calls the patient back 2 days after the initial visit. Which of the following would be an appropriate part of the data analysis following this experiment?

### 14.

A health insurance company conducts an experiment in conjunction with certain hospitals to determine whether a standard surgery protocol should be modified. For the analysis of the data, alpha is set in advance at 0.05 (5%). What does this mean?

### 15.

A large web retailer regularly conducts tests by randomly showing one of 5 price levels when a person shops. A marketing manager is concerned about imbalances in the page views of each price level and conducts a study in which N page views are examined and the price level shown in each of the N page views is noted. Which of the following is an appropriate step in a resampling procedure to assess whether the allocation of pricing views is truly random?

### 16.

Consider the two scatterplots shown – one relating baseball win/loss records to the payroll, the other relating training hours to work productivity. Guess at the correlation coefficient for each.

### 17.

Consider the scatterplot, below, of baseball payroll and win/loss record. If a linear regression were performed and a regression line fit, what would be the slope and intercept? Make a guess.

### 18.

Consider the baseball payroll data with a regression line added (see figure). How would you interpret, in meaningful real terms, the extension of the regression line in either direction so that it spans the entire graph?

### 19.

Consider the following regression equation relating pulmonary capacity, measured in peak expiration flow rate (f), to years of exposure to cotton dust (d): f = -4.2d +424. Which of the following is true?

### 20.

Consider the following output from regression software, relating data on pulmonary capacity, measured in peak expiration flow rate (f), to years of exposure to cotton dust (d): f = -4.2d +424; p-value <0.01 Which of the following is true?

### 21.

About you: Are you looking for a statistics course that offers academic credit? (Tracking question only – no right answer)