Learn by Doing
Some features of this activity may not work well on a cell phone or tablet. We highly recommend that you complete this activity on a computer.
Here are the directions, grading rubric, and definition of high-quality feedback for the Learn by Doing discussion board exercises.
A list of StatCrunch directions is provided at the bottom of this page.
Variables
- Math: Math SAT score
- Verbal: Verbal SAT score
- Credits: Number of credits the student is registered for
- Year: Year in college (1=Freshman, 2=Sophomore, 3=Junior, 4=Senior)
- Exercise: Time (in minutes) spent exercising in a typical day
- Sleep: Time (in hours) spent sleeping in a typical day
- Veg: Are you a vegetarian (yes, no, some)
- Cell: Do you own a smart phone (yes, no)
Data
If you have not done so already, download the cell-phones datafile. As always, if you are prompted to login, just close the prompt and continue with the download.
Upload the datafile into StatCrunch. Note: the symbol * in the spreadsheet indicates a missing value; this means that the associated individual did not answer the question.
Context
In 2015 college students at a large state university completed a survey about their academic and personal life. Questions ranged from “How many credits are you registered for this semester?” to “Would you define yourself as a vegetarian?”
The researcher randomly selected 325 students from the university; 312 responded to the survey.
Prompt
The cell-phone datafile is available in the Data section below.
Once again, here is the research question for this lab.
Based on a recent study, roughly 80% of college students in the U.S. own a smartphone. Is the proportion of smartphone owners lower at this university?
Respond to each of the following in your initial post.
- State your hypotheses in symbolic form and in words. (The following should be clear in your answer: the population of interest and the meaning of the proportion p in terms of the variable Cell.)
- StatCrunch uses a normal model to estimate the P-value probability. Verify that normality conditions are met.
- Use StatCrunch to conduct the hypothesis test. (directions)
Copy and paste the results (the StatCrunch output window) into your initial post. - Give your P-value and interpret its meaning as a conditional probability.
- State a conclusion that answers the research question. Use a significance level of 5%. (Your answer should include the P-value and reference the population and the variable Cell.)
One sample proportion hypothesis test:
Outcomes in : Cell
Success : yes
p : Proportion of successes
H0 : p = 0.8
HA : p ≠ 0.8
Hypothesis test results:
Variable | Count | Total | Sample Prop. | Std. Err. | Z-Stat | P-value |
---|---|---|---|---|---|---|
Cell | 243 | 310 | 0.78387097 | 0.022718473 | -0.70995229 | 0.4777 |