Study Design & Sampling Methods
What is the "gold standard" of study designs?
Randomized controlled trial
A questionnaire asks the following question:
Have you ever been told that you have asthma?
a. Yes
b. No
Is this variable qualitative or quantitative? And, is this variable nominal, ordinal, discrete or continuous?
Qualitative, nominal
Visual sheet
What type of distribution is shown above: normal, standard normal (i.e., z), sampling distribution of means, or t-distribution?
Standard normal (or, z) distribution)
We are interested in evaluating whether the mean height of young women is 63 inches.
State the null hypothesis of this claim.
The mean height of young women is 63 inches.
A random sample of children were selected from a local school and the following statistics were recorded for their vitamin D levels:
n=200
sample mean = 45 ng/mL
SD = 15 ng/mL
What is the point estimate of the vitamin D levels?
45 ng/mL
A statistics student obtains height and weight data by interviewing classmates, friends and family members.
What type of sampling method is being used: random, simple random, systematic, convenience, stratified, or cluster?
Convenience
What are the three measures of center?
Mean, median, and mode
You are given the formula P(-2.70 < z < 2.70) = 70%. What does this formula represent?
a. The 70th percentile of the normal distribution.
b. The middle 70% of a normal distribution.
c. The 70th percentile of the standard normal distribution.
d. The middle 70% of the standard normal distribution.
d. The middle 70% of the standard normal distribution.
We are interesting in evaluating whether the mean time to diagnosis of cancer among women is less than 1 year.
State the null hypothesis of this claim.
The mean time to diagnosis of cancer among women is 1 year.
A random sample of children were selected from a local school and the following statistics were recorded and calculated for their vitamin D levels:
sample mean = 45 ng/mL
95% confidence interval = 42.92 - 47.08
How confident are we that the sample mean is in the 95% confidence interval?
We are 100% confident that the sample mean is in the 95% confidence interval since the lower and upper bounds of the confidence interval are calculated as being equidistant from the sample mean by the margin of error.
A researcher gives a paper survey to all patients that came into an urgent care today to assess the relationship between health insurance coverage and urgent care utilization.
What type of study is being performed?
Cross-sectional study
A questionnaire asks the following question:
How old were you when you first drove a car?
Is this variable qualitative or quantitative? And, is this variable nominal, ordinal, discrete or continuous?
Quantitative, discrete
What type of distribution is shown above: normal, standard normal (i.e., z), sampling distribution of means, or t-distribution?
Normal distribution
We are interested in evaluating whether the mean height of young women is 63 inches.
State the alternative hypothesis of this claim and which type of test you would use to test this claim.
The mean height of young women is not 63 inches.
Two-tailed test because the mean height could be either lower or higher than 63 inches (the null hypothesis).
What is the corresponding alpha level of a 95% confidence interval?
A researcher is studying the effect of education on health and conducts a survey of 150 randomly selected workers from each of the following categories: less than high school diploma, high school degree, and more than a high school degree.
What type of sampling method is being used: random, simple random, systematic, convenience, stratified, or cluster?
Stratified
A questionnaire asks the following question:
How do you rate your experience with your primary healthcare provider?
a. Poor
b. Fair
c. Good
d. Very good
e. ExcellentIs this variable qualitative or quantitative? And, is this variable nominal, ordinal, discrete or continuous?
Qualitative, ordinal
Systolic blood pressure has a mean of 120 mmHg and a standard deviation of 10 mmHg. Using the Empirical Rule, what percentage of people have systolic blood pressure between 100 and 140 mmHg?
95%
We are interesting in evaluating whether the mean time to diagnosis of cancer among women is less than 1 year.
State the alternative hypothesis of this claim and which type of test you would use to test this claim.
The mean time to diagnosis of cancer among women is less than 1 year.
Left-tailed test because we are interested in evaluating whether the time to diagnosis of cancer is less than the null hypothesis (=1 year).
A random sample of children were selected from a local school and the following statistics were recorded for their vitamin D levels:
sample mean = 45 ng/mL
95% confidence interval = 42.92 - 47.08
Would the 99% confidence interval be wider or narrower than the 95% confidence interval? Why?
It will be wider than the 95% confidence interval because we would be more confident that the population (true) mean lies within its bounds.
A researcher recruits participants who have cancer and who do not have cancer. The researcher then asks these participants about their previous pesticide exposure.
What type of study is being performed?
Case-control study
Which of the following measures of variation is the strongest and why?
Coefficient of variation is the strongest measure of variation (others include range, standard deviation, and variance) because it is able to be used to compare the variation of variables with different units as it is unitless.
You are given the formula P(x < 54) = 80%. What does this formula represent?
a. The 80th percentile of a normal distribution.
b. The middle 80% of a normal distribution.
c. The 80th percentile of the standard normal distribution.
d. The middle 80% of the standard normal distribution.
a. The 80th percentile of a normal distribution.
When we perform statistical testing, which type of hypothesis is tested and which is tested against?
A random sample of children were selected from a local school and the following statistics were recorded and calculated for their vitamin D levels:
sample mean = 45 ng/mL
95% confidence interval = 42.92 - 47.08
Interpret the 95% confidence interval.
We are 95% confident that the population (true) mean vitamin D levels for children is between 42.92 ng/mL and 47.08 ng/mL.