10.1 D1

10.1 D1

How much does an Oreo weigh?

Mrs. Gallas wanted to estimate the average weight of an Oreo cookie to determine if the average weight was less than advertised. She selected a random sample of 30 cookies and found the weight of each cookie (in grams). The mean weight was 11.1921 grams with a standard deviation of 0.0817 grams. Make a 95% confidence interval to estimate the true mean weigh of an Oreo.

Fill in the Blanks

What is the point estimate for the true mean? (just type the number to four decimal places)

Open Ended

Identify the population and sample.

Open Ended

Identify the parameter and statistic.

Open Ended

3. Was the sample a random sample? Why is this important?

Multiple Choice

What is the formula for calculating the standard deviation of the sampling distribution of x-bar?

Multiple Choice

What condition must be met in order to use the formula for standard deviation?

• Random condition

• 10% condition

• Large Counts condition

Fill in the Blanks

In the formula for standard deviation of the sampling distribution for x-bar, we don't know the value of sigma (if we did, we would have known mu) so we will use Sx instead. Find the standard error. (to four decimal places 0.1234)

Multiple Choice

Would it be appropriate to use a normal distribution to model the sampling distribution of x-bar? Justify your answer.

• No, because the data is skewed.

• Yes, because it comes from a normally distributed population.

• Yes, because the sample size is 30 or greater.

• Yes, because the sample data is not skewed.

Multiple Choice

8. When finding the margin of error for a confidence interval for a proportion we use z*. For a mean we will use ______ as the critical value.

• a, b, c it's all greek to me!

• z

• X

• t

Fill in the Blanks

9. What t* is needed for this confidence interval? Use Table B and the degrees of freedom (df)=n - 1 to find it. (answer to 3 decimal places 0.123)

Fill in the Blanks

Calculate the margin of error using t* and the standard error from question 6. (answer to four places 0.1234)

Open Ended

11. Calculate the 95% confidence interval using PE +/- Margin of error.

Interpret the interval

We are 95% confident that the interval from 11.1616 to 11.2226 grams captures the true mean weight of all Oreos.

Specific Formula

Confidence Interval for a population mean

Multiple Choice

14. According to Nabisco, an Oreo weighs 11.3 grams. Does our CI provide convincing evidence that the true average weight is less than 11.3 grams?

• No. All the plausible values are less than 11.3 grams.

• Yes. All the plausible values are less than 11.3 grams.

• Yes. 11.3 grams is contained within our interval.

• No. 11.3 grams is not contained within our interval.

Fill in the Blanks

CYU 1a. Use Table B to find the critical value t* that you would use for a 98% CI based on a random sample of 26 observations. (round to three places after decimal 0.123)

Fill in the Blanks

Use Table B to find the critical value t* that you would use for a 99% confidence interval from an SRS of 85 observations. (round to three decimal places 0.123)