STAT CRUNCH Lab3 - Inferential Statistics Lab Spring 2022

Investigation: Strawberry Consumption

Blueberry consumption has increased dramatically in the last decade, but strawberries are still the number one berry in the United States. Annual strawberry consumption in the US is normally distributed with a mean of 7 lbs per person in 2015. Suppose that you want to decide whether last year's mean strawberry consumption has increased from the mean in 2015.

An excel table on blackboard provides last year's strawberry consumption, in pounds, for 21 randomly selected Americans. Follow the instructions below to upload this table and analyze the data to decide if the mean consumption of strawberries has increased since 2015.

Stat Crunch Portion of the lab:

1. Upload Report Data

• Go to Blackboard/StatCrunch/Report 2 and copy the Strawberry Data S22.xlsx file to your computer.
• Enter Mylab Statistics. Click on StatCrunch. Then click on "StatCrunch website"
• Under "Data" click on "Upload Data"
• Drag the Strawberry S22.xlsx file to the "Drag file here" area.
• Keep check mark on "First line as column name". Click Upload.

1. The default in StatCrunch is 8 significant digits for all results. We want to change this to 4. Click the drop-down menu for Edit and select "Display Precision". Under Results display choose 4 digits.
2. Use Stat Crunch to produce a table of descriptive summary statistics containing the mean, median (Q2), standard deviation, range, min, max, Q1, Q3, and IQR of the Grade Data.
   1. In Stat Crunch on the top row click on "Stat" "Summary Stats" "Columns"
   2. Under Select Column(s) (Ctrl-click) on each to select "Strawberry Consumption".
3. Under Statistics (Ctrl-click) on each to select: Mean, Std. dev., Median, Range, Min, Max, Q1, Q3, IQR.
4. Compute!

A table will appear with descriptive statistics for Strawberry Consumption. Remember the median is Q2.

1. Produce a 95% confidence interval for the population mean strawberry consumption.
   1. In Stat Crunch on the top row click on "Stat" "T Stats" "One Sample" "With Data"
   2. Under Select Column(s) select "Strawberry Consumption".
   3. Under Perform:select "Confidence Interval for ". Level "95%"
   4. Under Optional graphs and tables: select "Confidence interval plot"
2. In Stat crunch, you will now get information to perform a one-mean hypothesis t-test at the 5% significance level to test if Strawberry consumption has significantly increased since 2015.
   1. In Stat Crunch on the top row click on "Stat" "T Stats" "One Sample" "With Data"
   2. Under Select Column(s) select "Strawberry Consumption".
   3. Under Perform:select "Hypothesis test for " with null = "7" and alternative as ">"

Steawberry data S22.xlsx file

Strawberry Consumption

8.86

7.21

8.65

9.29

9.48

7.83

6.14

6.26

6.45

7.17

7.23

7.36

7.97

8.00

7.95

7.71

7.38

6.69

7.12

6.80

8.50

Final Report and Questions

On the first page of your report, include an introduction with your name, class, date, title of lab and a short description of the lab. After the introduction, copy and paste 4 things from Stat Crunch: 1) Table of Summary Statistics, 2) Confidence interval table, 3) Confidence interval plot, and 4) Hypothesis test table. Use statistics from your tables of information to answer the following questions. Use complete sentences when appropriate and show work as required.

1. Use your Summary Statistics table:
   1. What are the mean and median of your sample?
   2. What is the standard deviation of your sample?
2. Use your Confidence Interval table and confidence interval plot.
   1. Interpret the confidence interval for this data. (i.e., "I am 95% confident...")
   2. Based upon this confidence interval, do you think the mean consumption of Strawberries is now above 7 lbs.? For credit Use the interval in your reasoning.
3. Use your Hypothesis test table:

At the 5% significance level, do the data provide sufficient evidence to conclude that Strawberry consumption has increased significantly over the previous mean of 7 lbs.?

Write out the 6 steps of the hypothesis test. Use the test statistic "t" and p-value you get from the table you produced in STAT CRUNCH step 3. Do not calculate your test statistic or attempt to lookup your P-value just use the values from your table. No credit for using critical value analysis.

1. Hypotheses
2. Alpha
3. Test Statistic
4. P value
5. Reject or Do not Reject the null hypothesis based upon the P value. No credit for using critical value technique here.
6. Interpret.
7. Give strength of your evidence.