1-5 Questions
In a recent study on work patterns, researchers analyzed data from the American Time Use Survey, which collects detailed 24-hour time diaries from a large sample of U.S. adults each year. The study focused on workers in occupations with high exposure to generative AI tools like ChatGPT, comparing their time use before and after these tools became widely available. Researchers found that workers in jobs with high AI exposure actually worked about 3 hours more per week after the AI tools like ChatGPT became widely available.
Identify the population and sample.
Population: all working U.S. adults
Sample: the U.S. adults in the study who completed the 24-hour time diaries
Does a Mediterranean diet during pregnancy improve child neurodevelopment at age 2 years?
A study was conducted involving 1,221 pregnant women. The women were randomly assigned into three groups for four weeks during their pregnancies: a Mediterranean diet intervention, a stress reduction program, and usual prenatal care with no interventions. A total of 626 children were assessed at age 2 years and it was determined that children in the Mediterranean diet group had higher scores in the cognitive domain and social-emotional domain than in the usual care group.
Based on the results, can the researchers conclude that the eating a Mediterranean diet during pregnancy caused higher scores? Explain.
Yes, because this is an experiment with random assignment of pregnant women to different diets.
Gallup is an organization that collects and shares information about public opinion. Kentwood Public Schools partnered with Gallup to create a survey for teachers in the district. The survey was sent out through email to a random sample of 100 teachers, with 56 teachers responding.
One of the questions was “How much time do you have for planning each day?”. For the 56 teachers that responded, the average amount of time was 85 minutes.
Do you think the average amount of time for planning for the teachers in the sample is greater than or less than the true average amount of time for planning for all 100 teachers? Explain.
Greater than. The teachers that didn’t respond to the survey were more likely to be too busy, possibly because they have less time for planning each day than those teachers who did have the time to respond.
Difference between systematic random sampling and stratified random sampling.
Systematic selects individuals in intervals after a random starting point. Stratified divides population into groups and then randomly samples within each group.
Does the wording of a request impact children’s willingness to help? Researchers wondered if referring to a child as a “helper” or asking a child to “help” would affect their behavior. Participants were 51 four- and five-year old children who were randomly assigned to one of three groups. 17 children were assigned to the “verb condition” by asking them to help pick up toys, 17 children were assigned to the “noun condition” by asking them to be helpers when picking up toys, and the remaining 17 children were assigned to a baseline group (without using help or helper). Researchers then measured the number of toys children picked up after being given the directions. The children who were assigned the noun condition (helper) helped significantly more than the children in the other two groups.
Identify the experimental units.
51 four- and five-year old children
Name one way that a cluster random sample is the same as a stratified random sample.
For both sampling methods, the population is split into groups (clusters or strata).
Applying a new medicated hand cream is expected to reduce dry skin. In an experiment to assess reduction in dry skin, volunteer patients will be randomly assigned to one of two treatments. One group will apply the new medicated hand cream and the other group will apply a placebo that looks identical to medicated hand cream but does not contain any medicine. Each patient will then be evaluated by a doctor to determine how much dry skin is present. The doctor recording the data is unaware of whether the patient received the medicated hand cream or the placebo.
Which statement best explains blinding for this scenario?
A) Both the patient and the doctor are blind to the treatment.
B) Neither the patient nor the doctor is blind to the treatment.
C) The patient is blind to the treatment, but not the doctor.
D) The doctor is blind to the treatment, but not the patient.
A
Gallup is an organization that collects and shares information about public opinion. Kentwood Public Schools partnered with Gallup to create a survey for teachers in the district. The survey was sent out through email to a random sample of 100 teachers, with 56 teachers responding.
One of the questions was “How much time do you have for planning each day?”. For the 56 teachers that responded, the average amount of time was 85 minutes.
Does this scenario describe a voluntary response sample, nonresponse, or both? Explain.
Nonresponse bias. Of the 100 teachers selected to be the sample, 44 did not respond. It is not voluntary response because there was an intentional sample of 100 teachers, not an open invitation to all teachers.
Researchers recruited a sample of pregnant women from prenatal care practices in Connecticut for a study about chocolate intake during pregnancy. The women were interviewed during their first and third trimesters about risk factors for preeclampsia, an adverse pregnancy outcome, and their chocolate consumption. Women who reported regular chocolate consumption of one to three servings per week had a 50 percent reduced risk of preeclampsia.
Is the scenario described an observational study or an experiment? Explain.
The scenario is an observational study because treatments were not imposed on the pregnant women. The researchers asked the women about their chocolate consumption and did not assign them to either eat chocolate or not eat chocolate.
A gardener tests whether a new LED grow light changes basil growth. She has 36 basil seedlings of the same variety and age. Twelve are randomly assigned to a standard fluorescent light, 12 to the LED at low intensity, and 12 to the LED at high intensity. All 36 get the same pot size, soil, watering schedule, and room temperature. After 4 weeks she records each plant's height in centimeters.
What are the treatments?
The lighting variable has three levels (fluorescent, LED low, LED high), so there are 3 treatments
A new ridesharing company called OoberLift wants to survey their customers about their rideshare experience with the company. Using the app, they send the following request:
Our users have consistently had very positive experiences with OoberLift. We will always continue to strive for perfect 5-star reviews! What is your rating for your experience?
Name two potential sources of bias present in this survey. Explain.
Question wording bias – the survey includes additional information that is leading.
Response bias – users might lie and rate their experience higher than the truth because they don’t want to disappoint the company.
What is the main difference between a completely randomized design and a randomized block design?
In a completely randomized design, treatments are assigned to experimental units completely at random. In a randomized block design, experimental units are separated into groups (blocks) by a common characteristic that is thought to affect the response to a treatment. Then treatments are assigned completely at random within each block.
A middle school band teacher assigns students to practice their instruments at home for 15 minutes per day. Students are required to keep a “practice log” where they record the number of minutes they practice each day. The teacher selects a random sample of 10 practice logs and finds the average amount of practice per day is 17.8 minutes.
Name one potential source of bias present in this survey. Explain.
Response bias. Because students are self-reporting their practice times, they may not be truthful.
Does a Mediterranean diet during pregnancy improve child neurodevelopment at age 2 years?
A study was conducted involving 1,221 pregnant women. The women were randomly assigned into three groups for four weeks during their pregnancies: a Mediterranean diet intervention, a stress reduction program, and usual prenatal care with no interventions. A total of 626 children were assessed at age 2 years and it was determined that children in the Mediterranean diet group had higher scores in the cognitive domain and social-emotional domain than in the usual care group.
Is the study described an observational study or an experiment? Explain.
The study is an experiment because the women were randomly assigned into one of three treatment groups: Mediterranean diet, stress reduction, or nothing.
To examine the efficacy of a speech pathology program, a group of 50 children was split into two groups. One group of children received speech services once a week for ten weeks and the other group received speech services twice a week for ten weeks. At the end of the ten weeks, each child was tested and the number of speech errors they made was recorded.
What is the response variable?
The response variable is the number of speech errors made during testing.
Question 4 on Packet.
C. unbiased estimator
A physical therapist plans to conduct an experiment using a randomized block design with patients from her clinic to determine the effectiveness of two different exercises on reducing joint pain and increasing mobility. She is considering two variables to create the blocks: age of the patients (under 50 years old and 50 or more years old) and time of appointment (morning and afternoon).
Which variable should be chosen to create the blocks? Why?
The age of the patients should be chosen to create the blocks because age is more likely to have an impact on joint pain and mobility in physical therapy patients.
Each Major League Baseball (MLB) team is allowed to have 26 players on their roster for opening day. With 30 MLB teams, this means there are 780 players on the opening day rosters. An avid baseball fan wants to select a random sample of these players.
Describe a method that could be used to select a systematic random sample of 78 players.
Label each player with a unique number from 1 to 780. Use a random number generator to generate one number between 1 and 10. The player that corresponds to this number is the first player selected. Then select every 10th player that is past this player on the list until 78 players are selected.
Researchers recruited a sample of pregnant women from prenatal care practices in Connecticut for a study about chocolate intake during pregnancy. The women were interviewed during their first and third trimesters about risk factors for preeclampsia, an adverse pregnancy outcome, and their chocolate consumption. Women who reported regular chocolate consumption of one to three servings per week had a 50 percent reduced risk of preeclampsia.
Identify the response and explanatory variables.
The explanatory variable is the amount of chocolate consumed during pregnancy.
The response variable is whether or not the women developed preeclampsia before giving birth.
A statistics teacher wants to conduct a study with her students to determine if completing a review sheet is an effective way to prepare for a test. She has 180 students and would like to randomly assign half of them to complete a review sheet made by the teacher and the other half to study on their own.
Describe a process that would randomly assign the 180 students to the two treatment groups.
Assign each student a unique number between 1 and 180. Use a random number generator to select 90 numbers between 1 and 180 (no repeats). Give the students corresponding to the numbers selected a review sheet to complete before the test. The remaining 90 students will prepare for the test on their own.
Does the wording of a request impact children’s willingness to help? Researchers wondered if referring to a child as a “helper” or asking a child to “help” would affect their behavior.
Participants were 51 four- and five-year old children who were randomly assigned to one of three groups. 17 children were assigned to the “verb condition” by asking them to help pick up toys, 17 children were assigned to the “noun condition” by asking them to be helpers when picking up toys, and the remaining 17 children were assigned to a baseline group (without using help or helper). Researchers then measured the number of toys children picked up after being given the directions. The children who were assigned the noun condition (helper) helped significantly more than the children in the other two groups.
Identify the treatments.
Verb condition (help), noun condition (helper), baseline condition (neither)
In an experiment full of volunteers can I generalize the results to the whole population? True or False
False, I can only generalize the results to people similar to those in the experiment.
A local Amazon distribution center delivers products to three different states: Illinois, Michigan, and Ohio. There were 14,500 purchases delivered from this distribution center on one day. Amazon wants to send a customer service survey to a sample of 100 customers who got one of these deliveries.
How could Amazon ensure that customers from all three states are represented in the survey? Explain.
Select a stratified random sample, using the three states as the strata. With an SRS from each group, Amazon would ensure that customers from all three states will be represented in the sample.
A confounding variable is an extra...
hidden cause.
With random assignment, you can conclude _____ relationship/conclusion.
cause-and-effect.