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

Confidence Intervals!Sample size!

When do you use

t* values z* values

What do you need to know to find the value.

What do you need to know to find the value

When do you use

t* values z* 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

When do you use

t* values z* 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

Confidence level (Degrees of freedom (n-1)

Confidence level (

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?

A box of Lucky Charms promises an average 15 oz of cereal per box. You want to test this claim, so you tested a sample of n boxes. The average amount of cereal in these n boxes was 13 oz with an estimated = 1.8oz.

What are some ways you can make your confidence interval…

Narrower Wider

What are some ways you can make your confidence interval…

Narrower Wider

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?

What are some ways you can make your confidence interval…

Narrower Wider

• Increase n

• Decrease confidence

• Decrease n

• Increase confidence

Determining sample size

Determine what you want your margin of error to be. What is margin of error. How does it relate to your confidence interval

width

.

What is…nZ*

m

16oz cans of pepsi are filled with a dispense valve that has a fill standard deviation of 1.2 oz.

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)

Which sentences properly Interpret this confidence interval???

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…

( 96.9 99.3)