Download Name: Directions: For full credit, fill in the 6 tables on the Excel

Name:
Directions:
For full credit, fill in the 6 tables on the Excel Spreadsheet and complete the questions below. You do not need to
use Excel formulas to answer questions, but it is recommended. Turn in the excel sheet and these pages STAPLED
when we return to class on the 22nd. You do not need to type your answers. Do not email the answers. Late
assignments will receive 0 credit.
Question 1:
We are interested in predicting the mean grade of the entire class on the first exam. We have learned that one way
to predict the population mean is to choose a sample and compute a confidence interval using the sample mean. To
illustrate this, I used each of the seven lab classes to represent a sample of the population. We will be calculating a
confidence interval for each lab group.
Step 1: Looking at the data:
Create a dot plot or histogram for at least 2 of the 7 labs. Use each possible grade as a bin (70, 75, 80, 85, etc.)
Label your plots and comment on the shape of the distributions. Do they look like normal distributions?
Step 2: Finding the sample statistics:
Compute the mean, standard deviation, and sample size of each class and record your results on the Excel
Spreadsheet. (Hint: You can use the =AVERAGE() and =STDEV.S(), or STDEV functions in Excel to quickly
calculate these. Which lab group had the highest sample mean? Does there appear to be much variability in the
means between classes?
Step 3: Computing the values to be used in the confidence interval:
Find the appropriate t-value or Z-value for a 95% confidence interval record it in the appropriate row. Compute the
Standard Error for each class and record your results on the Excel Spreadsheet. Do these “samples” merit a large
sample or small sample confidence interval? Which table, Z or t, should be used?
Step 4: Computing the Confidence Intervals
Using your sample means, test values, and standard errors, find the lower and upper bounds of each of the
confidence intervals for the population mean and record your results on the excel spreadsheet. Plot the endpoints
and sample mean and draw a line representing each of the confidence intervals. How many of the confidence
intervals captured the true mean test grade of the class (.8406%)?
.8406
A
Name:
Question 2:
I have randomly selected 10 of the grades from each lab group. Repeat the steps below.
Step 2: Finding the sample statistics:
Compute the mean, standard deviation, and degrees of freedom of each class and record your results on the Excel
Spreadsheet. (Hint: You can use the =AVERAGE() and =STDEV() functions in Excel to quickly calculate these.
Which lab group had the highest sample mean? Does this differ from the previous question?
Step 3: Computing the values to be used in the confidence interval:
Find the appropriate t-value or Z-value for a 95% confidence interval record it in the appropriate row. Compute the
Standard Error for each class and record your results on the Excel Spreadsheet. Do these “samples” merit a large
sample or small sample confidence interval? Which table, Z or t, should be used?
Step 4: Computing the Confidence Intervals
Using your sample means, test values, and standard errors, find the lower and upper bounds of each of the
confidence intervals for the population mean and record your results on the excel spreadsheet. Draw a line
representing each of the confidence intervals. How many of the confidence intervals captured the true mean test
grade of the class (.8406%)?
.8406