Statistics for Decision Making Solution 2022

1
MATH221 Statistics for Decision Making
Week 6 Lab
Name: _______________________
Statistical Concepts:
 Confidence Intervals
 Data Simulation
 Normal Probabilities
Short Answer Writing Assignment
All answers should be complete sentences.
In the Week 2 Lab, you found the mean and the standard deviation for the SLEEP
variable for both males and females. Use those values for follow these directions to
calculate the numbers again.
(From Week 2 Lab: Calculate descriptive statistics for the variable Sleep by Gender.
Sort the data by gender by clicking on Data and then Sort. Copy the Sleep of the
males from the data file into the Descriptive Statistics worksheet of the Week 1 Excel
file. [Write down the mean and standard deviation.] These are sample data. Then,

2
copy and paste the female data into the Descriptive Statistics workbook and do the
same. Keep three decimal places.)
You will also need the number of males and the number of females in the dataset. You
can actually count these in the dataset.
Then use the Week 5 spreadsheet to calculate the following confidence intervals. The
male confidence interval would be one calculation in the spreadsheet and the females
would be a second calculation.
Solution
Statistics obtained for female are:
Female
Mean 6.824
Standard deviation 1.237
Sample size 17
The statistics obtained for male are:
Male
Mean 7.556
Standard deviation 1.504
Sample size 18

3
1. Give and interpret the 95% confidence intervals for males and a second 95%
confidence interval for females on the SLEEP variable. Which is wider and why?
Solution
The confidence intervals calculated above show that at 95% level of confidence the true mean for
the hour of sleep for the male gender is between 6.808hours and 8.303hours. On the other hand, at
95% confidence level the exact mean for the hours of sleep in female gender range from 6.188hours
to 7.459hrs (Linoff, 2014).