StatCrunch - Assignment #5
Part One: Calculate the mean and standard deviation of a random variable.
Calculate the mean and standard deviation of a random variable.
Load the data from problem #100 (below) where Y = the number of people waiting in
line at a fast food restaurant at 10 am.
Calculate a new y * P(y) column by highlighting “var 3” and clicking Data > Compute
Expression. Click the blue “Build” button. Select “y” and click “Add Column”. Click
the “*” button. Select “P(y)” and click “Add Column”. Then click “Okay”. Lastly click
“Compute!” and the new column will be generated.
To get the Mean sum the new y * P(y) column. Highlight “var4” and again click Data >
Compute Expression. Click the blue “Build” button. Scroll down the Functions list,
select “sum” and click “Add Function”. Select “y * P(y)” in the Columns list and click
“Add Column”. Then click “Okay”. Lastly click “Compute!” and the sum (mean) will
be generated as the only value. Rename the new column as Mean.
Next calculate a new (y - µ)^2 * P(y) column by highlighting “var 5” and clicking Data
> Compute Expression. Build the expression and use µ = the mean value you just
calculated.
To get the standard deviation highlight “var6” and click Data > Compute Expression.
Start with the function “sqrt” then do “sum” and lastly do the column you just made.
Click “Okay” and check that your expression is correct, then click “Compute!”. Rename
this new column (with a single value) as “Std Dev”. Save your data so you can show it in
your Report.
Part Two: Flipping a coin
Statcrunch has a nice calculator for computing binomial probabilities: Stat > Calculators
> Binomial. Let X = the number of heads when 20 honest coins are flipped.
1) Find P(X = 10)
2) Find P(X = 15)
3) Find P(X <= 15)
4) Find P(X > 15)
5) Find P(8 <= X < 17) This requires two Statcrunch calculations, then calculate the
final answer by hand and show it in your report.