When the sample is selected by picking people based on their position on a list using a sampling interval, what type of sampling is being done?

A researcher is curious to see if the amount of time spent on social media influences how often friends meet in person to socialize.  After their sample is selected the researcher asks the subjects on average how much time they spend on social media each day and then asks their subjects to keep track of how many times they meet in person with their friends to socialize and report back at the end of the month.  What type of study design is this?

A researcher is curious to see if the amount of time spent on social media influences how often friends meet in person to socialize.  After their sample is selected the researcher tells half the sample to spend at least 4 hours each day on social media and the other half to spend no more than 4 hours on social media each day.  Then to report back at the end of the month how many times they meet in person with their friends to socialize.  What type of study design is this?

Based on the following research question: Does having diabetes lead to people increasing the average number of servings of fruit they normally eat per day?   The variable average number of servings of fruit eaten per day is the [answer1] The variable having diabetes is the [answer2]

A student at a college administers a survey to estimate the average number of miles driven weekly among on-campus students at USF. The student sends a questionnaire to the 35th person in each sampling interval, from a complete list of on-campus students provided by the registrar. What type of sampling has occurred?

Based on a sample 100 great white sharks the average length is roughly 15 feet.  15 feet is a statistic.

3 students apply to a PhD program.  The program rejects 25% of all applicants.  Students are accepted and rejected independently of each other.  Let the random variable X represent the number of the 3 students who get rejected into the PhD Program. (Hint: Binomial distribution with n=3, P=25%)   What is the standard deviation of the random variable?  (round your answer to 4 decimal places)

If a researcher only contacts students who take their class to be a part of their sample, what type of sampling has occurred?

Five hundred women are enrolled in a study to evaluate the accuracy of a test for pregnancy. 200 of the women were actually pregnant. 170 of the pregnant women had a positive test as did 140 of the women who were not pregnant. What is the probability (i.e., specificity) that a woman tested negative on a test given that she is not pregnant? Test                         Pregnant? Yes No Total + 170 140 310 – 30 160 190 Total 200 300 500

Based on the following research question: Does playing video games make someone more likely to pursue a degree in a STEM field?   The variable do you play video games [answer1] The variable pursuing a degree in a STEM field [answer2]