t* valuesz* values What do you need to know to find the value. What do you need to know to find the value.

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Presentation transcript:

t* valuesz* values What do you need to know to find the value. What do you need to know to find the value

t* valuesz* values When you don’t know the population standard deviation When you use the sample standard deviation. When you know the population standard deviation What do you need to know to find the value. What do you need to know to find the value

t* valuesz* values When you don’t know the population standard deviation When you use the sample standard deviation. When you know the population standard deviation What do you need to know to find the value. What do you need to know to find the value

 Create a 95% confidence interval for your estimated average for n=40, and n=100.  Create a 90% confidence interval for your estimated average for n=40, and n=100  Do you think the company is holding up to their promise?

NarrowerWider

NarrowerWider What in the equation do you have control over?? Do you want to make the margin of error bigger or smaller? What in the equation do you have control over?? Do you want to make the margin of error bigger or smaller?

NarrowerWider Increase n Decrease confidence Decrease n Increase confidence

What is… n Z* m

a) Create a 95% confidence interval if you sample 25 bottles and get a sample average of 15.2oz. a) Interpret this confidence interval as you would report it to the manager. b) How large of a random sample is necessary so that your estimation of a mean bottle volume is within 2oz. (use 95% confidence) c) What if a manager wants to insure accuracy within 0.5 ounces. How large would your sample size need to be then. (use 95% confidence)

 I am 95% confident the average body temperature of an American is between 96.9 and 99.3 degrees.  95% of Americans have a body temperature between 96.9 and 99.3 degrees  The average body temperature of an American is between 96.9 and 99.3 degrees.  95% of samples have an average between 96.9 and 99.3  95% of confidence intervals from the samples I take will contain the true average American body temperature. In trying to predict average body temperature of Americans, I got a 95% confidence interval of… ( )