Question 1

How does the shape of the sampling distribution of means with sample sizes of N=10 and N=100 differ? How are they the same?

Accepted Answer

The shape of a sampling distribution with N=10 is wider than that of N=100 because the variability in the sampling distribution for the N=10 samples is much larger than the variability for the N=100 samples. They are the same because they have the same overall shape (bell-curve) and the peaks will still be located in the same place.

Question 2

In preparing a grant, you meet with a biostatistician to discuss sample sizes. The biostatistician tells you that if you want more power, you will have to increase your sample size. Explain why this is the case. Provide additional alternatives for increasing the power of the study without changing the sample size.

Accepted Answer

As the sample size gets larger, the alternative sampling distribution gets skinnier. As a result, the null and alternative distributions become more separated. When there is a discernable difference between the two distributions, it is easier to reject the null hypothesis correctly, and thus increases the power of the study. Alternatively, as the a level increases, the statistical power also increases.

Question 3

Suppose an investigator is comparing different infertility treatments. She hypothesizes that treatment A is better than treatment B. Describe what type 1 and type 2 errors would mean in this situation.

Accepted Answer

The null hypothesis is that there is no difference in the treatment. A type 1 error means that the conclusion is that A is better than B when they are the same. A type 2 error means that the conclusion is that A is the same as B when A is actually better.

Question 4

Central limit theorem states that the distribution of _________ will be normally distributed with large enough samples regardless of the shape of the population distribution.

Accepted Answer

A)  a sample size 
B)  sample means 
C)  a continuous random variable 
D)  a discrete random variable 
A)  a sample size 
B)  sample means 
C)  a continuous random variable 
D)  a discrete random variable

Question 5

Which of the following is most likely a type 2 error?

Accepted Answer

A)  Correctly concluding that an effect exists. 
B)  Correctly concluding that no effect exists. 
C)  Falsely concluding that an effect exists. 
D)  Falsely concluding that no effect exists. 
A)  Correctly concluding that an effect exists. 
B)  Correctly concluding that no effect exists. 
C)  Falsely concluding that an effect exists. 
D)  Falsely concluding that no effect exists.

Question 6

Suppose you are told that your BMI is 32, the 70th percentile for your age and sex. Interpret this percentile.

Accepted Answer

This means that among 100 peop

Question 7

An outbreak of food poisoning occurred at a high school a few hours after 100 students ate lunch at the school's cafeteria. Most of them developed symptoms including nausea, vomiting, and diarrhea. An investigation was conducted to identify the contaminated food source. Interviews were conducted with students who ate at the cafeteria, and a food history was collected. Describe this study design (case-control, cohort, cross-sectional). Explain.

Accepted Answer

A cohort study would not be appropriate

Question 8

A study was conducted to investigate whether the use of vitamins during prostate cancer treatment would improve the prostate-specific antigen (PSA). PSA in study patients was measured before treatment and four months after treatment. Suppose the change in PSA is 3.0 and there is a p-value of 0.07. How would you interpret this result?

Accepted Answer

When a p-value is considered small but s

Question 9

Consider a study where the majority of the study subjects have high body mass index (BMI) and only a few have low BMI. When a histogram is constructed to describe the distribution of BMI, what shape of the distribution is most likely to be observed (right-skewed, left-skewed, or symmetric)?

Accepted Answer

The distribution would be left

Question 10

Twenty fibromyalgia patients are asked to register their pain on a visual analog scale (VAS), where 0 represents no pain and 5 represents the worst pain imaginable. The responses are {0, 0, 0, 1, 1, 2, 2, 3, 3, 3, 4, 4, 4, 4, 4, 5, 5, 5, 5, 5}.a.What are the frequency distribution and probability distribution of this sample? b.What are the mean, median, and mode for the VAS?

Accepted Answer

a.The frequency distribution of the VAS

Question 11

In the following scenarios, state which type of error (type 1 or type 2) you would want to change in a hypothesis test to reduce errors.
A)You are investigating an effect of drug A indicated for patients who risk death if not treated. The drug will be used to replace a therapy that has serious side effects. The study is testing the hypotheses:
Null hypothesis: drug A is not effective.
Research hypothesis: drug A is effective. 
B)Many studies are investigating different experimental strategies for increasing bone density in osteoporotic women. Suppose a new therapy has been discovered to increase bone density in mice. It is possible that this therapy could be effective in humans.
The study is testing the hypotheses:
Null hypothesis: drug A is not effective.
Research hypothesis: drug A is effective.

Accepted Answer

A)You would consider decreasing type 1 e

Question 12

A study was conducted to examine the gender difference in daily smoking prevalence.
A)State the null and research hypotheses for this test.
B)Suppose the p-value associated with the test is 0.04. What can you conclude?

Accepted Answer

a.Research hypothesis: there is a differ

Question 13

You suspect that the salary of study participants might be skewed. A statistician told you that the skewed data should not be described by a mean. Why?

Accepted Answer

In a skewed data set, the mean

Question 14

A 2-year study was conducted to investigate bicycle safety at a city's 10 most congested intersections. The primary variable of interest was the number of accidents that involved a bicycle. Describe the number of accidents involving a bicycle as a continuous and ordinal variable.

Accepted Answer

The number of bicycle accidents can be c

Question 15

Briefly describe the difference between a bar graph and a histogram. Consider your own area of interest. Provide an example where a bar graph would be most appropriate. Provide an example where a histogram would be most appropriate.

Accepted Answer

A bar graph is often used to show the vi

Question 16

Which of the following statements is considered a null hypothesis?

Accepted Answer

A)  The children who watch more than 2 hours of TV have the same weight gain as children who watch TV less than 2 hours. 
B)  Smoking is related to poorer health status. 
C)  There is a greater amount of fatigue in health-care professionals in urban areas. 
D)  Increases in activity are associated with decreases in cognition. 
A)  The children who watch more than 2 hours of TV have the same weight gain as children who watch TV less than 2 hours. 
B)  Smoking is related to poorer health status. 
C)  There is a greater amount of fatigue in health-care professionals in urban areas. 
D)  Increases in activity are associated with decreases in cognition.

Question 17

John waited 30 minutes to be treated in an emergency room. A 30-minute wait is in the 20th percentile of the wait time. Did he have a comparatively long- or short wait time? Interpret this percentile.

Accepted Answer

John had a short wait time. In

Question 18

Power, type 1 and type 2 errors are all related, which of the following statements is NOT true?

Accepted Answer

A)  Probability of type 2 error = 1-power. 
B)  If the probability of type 1 error increases, the power also increases. 
C)  Probability of type 1 error is inversely related to the probability of type 2 error. 
D)  Probability of type 1 error increases with the probability of type 2 error. 
A)  Probability of type 2 error = 1-power. 
B)  If the probability of type 1 error increases, the power also increases. 
C)  Probability of type 1 error is inversely related to the probability of type 2 error. 
D)  Probability of type 1 error increases with the probability of type 2 error.

Question 19

Which of the following is NOT an advantage of a retrospective study?

Accepted Answer

A)  Sample size required is relatively small compared to that of a prospective study. 
B)  Efficient when the outcome is rare. 
C)  Efficient when the outcome requires a long time to develop. 
D)  Investigators have control over the way the variables are collected. 
A)  Sample size required is relatively small compared to that of a prospective study. 
B)  Efficient when the outcome is rare. 
C)  Efficient when the outcome requires a long time to develop. 
D)  Investigators have control over the way the variables are collected.

Question 20

A group of investigators are interested in conducting a clinical trial to determine whether taking bio-identical treatments prevents postmenopausal osteoporosis in women. They obtained a list of physicians in the region and recruited their patients by mailing out response cards to all eligible women; 60% of the cards were returned and 75% of those respondents entered the study. They were equally divided into the treatment group and placebo group, and were followed for 5 years to determine if they develop osteoporosis. Identify the population, sample, sampling frame, and type of study.

Accepted Answer

Population: all postmenopausal women in

How does the shape of the sampling distribution of means with sample sizes of N=10 and N=100 differ? How are they the same?

Suppose an investigator is comparing different infertility treatments. She hypothesizes that treatment A is better than treatment B. Describe what type 1 and type 2 errors would mean in this situation.

Central limit theorem states that the distribution of _________ will be normally distributed with large enough samples regardless of the shape of the population distribution.

Which of the following is most likely a type 2 error?

Suppose you are told that your BMI is 32, the 70th percentile for your age and sex. Interpret this percentile.

Consider a study where the majority of the study subjects have high body mass index (BMI) and only a few have low BMI. When a histogram is constructed to describe the distribution of BMI, what shape of the distribution is most likely to be observed (right-skewed, left-skewed, or symmetric)?

A study was conducted to examine the gender difference in daily smoking prevalence. A)State the null and research hypotheses for this test. B)Suppose the p-value associated with the test is 0.04. What can you conclude?

You suspect that the salary of study participants might be skewed. A statistician told you that the skewed data should not be described by a mean. Why?

A 2-year study was conducted to investigate bicycle safety at a city's 10 most congested intersections. The primary variable of interest was the number of accidents that involved a bicycle. Describe the number of accidents involving a bicycle as a continuous and ordinal variable.

Briefly describe the difference between a bar graph and a histogram. Consider your own area of interest. Provide an example where a bar graph would be most appropriate. Provide an example where a histogram would be most appropriate.

Which of the following statements is considered a null hypothesis?

John waited 30 minutes to be treated in an emergency room. A 30-minute wait is in the 20th percentile of the wait time. Did he have a comparatively long- or short wait time? Interpret this percentile.

Power, type 1 and type 2 errors are all related, which of the following statements is NOT true?

Which of the following is NOT an advantage of a retrospective study?

Continuous Data- Making Comparisons

Continuous Data: Correlation and Regression

Categorical Data: Comparisons and Associations

A Dichotomous Outcome: Confounding and Regression

Count Data

Time to Event Data

Filters

Exam 1: An Overview of Statistical Concepts

How does the shape of the sampling distribution of means with sample sizes of N=10 and N=100 differ? How are they the same?

Suppose an investigator is comparing different infertility treatments. She hypothesizes that treatment A is better than treatment B. Describe what type 1 and type 2 errors would mean in this situation.

Central limit theorem states that the distribution of _________ will be normally distributed with large enough samples regardless of the shape of the population distribution.

Which of the following is most likely a type 2 error?

Suppose you are told that your BMI is 32, the 70th percentile for your age and sex. Interpret this percentile.

Consider a study where the majority of the study subjects have high body mass index (BMI) and only a few have low BMI. When a histogram is constructed to describe the distribution of BMI, what shape of the distribution is most likely to be observed (right-skewed, left-skewed, or symmetric)?

A study was conducted to examine the gender difference in daily smoking prevalence. A)State the null and research hypotheses for this test. B)Suppose the p-value associated with the test is 0.04. What can you conclude?

You suspect that the salary of study participants might be skewed. A statistician told you that the skewed data should not be described by a mean. Why?

A 2-year study was conducted to investigate bicycle safety at a city's 10 most congested intersections. The primary variable of interest was the number of accidents that involved a bicycle. Describe the number of accidents involving a bicycle as a continuous and ordinal variable.

Briefly describe the difference between a bar graph and a histogram. Consider your own area of interest. Provide an example where a bar graph would be most appropriate. Provide an example where a histogram would be most appropriate.

Which of the following statements is considered a null hypothesis?

John waited 30 minutes to be treated in an emergency room. A 30-minute wait is in the 20th percentile of the wait time. Did he have a comparatively long- or short wait time? Interpret this percentile.

Power, type 1 and type 2 errors are all related, which of the following statements is NOT true?

Which of the following is NOT an advantage of a retrospective study?

Continuous Data- Making Comparisons

Continuous Data: Correlation and Regression

Categorical Data: Comparisons and Associations

A Dichotomous Outcome: Confounding and Regression

Count Data

Time to Event Data

Filters