B Heard

Lecture for the Week 6 Lab

Statistics For Decision Making

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There are four parts to the lab this week:Part 1: Normal Distributions and Birth

Weights in AmericaPart 2: Central Limit Theorem and Age

Distributions in the United StatesPart 3: Finding z and t scores for Confidence

IntervalsPart 4: Bob’s Candies (Using Confidence

Intervals to decide a course of action)

Week 6 Lab

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Week 6 Lab

Part 1……….

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Birth Weights in America

Week 6 Lab

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Week 6 Lab

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Birth Weights in America, Number 1, part a

You can see that the graph has a mean of less than 7.5, so the 37 to 39 Weeks Gestation period is the obvious choice.

Birth Weights in America, Number 2, part b

We will identify the mean birth weight and standard deviation for the 32 to 35 week gestation period for this problem.

The mean is 5.73 lbs and the standard deviation is 1.48 lb.

Week 6 Lab

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Birth Weights in America, Number 2, part b continued

Using the NORMDIST function with the point in question, the mean, the standard deviation, and the cumulative value “TRUE” gives the percent of babies under 5.5 lbs. The distribution “fills” from left to right.

Week 6 Lab

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Birth Weights in America, Number 3, part b

We will identify the mean birth weight and standard deviation for the over 42 weeks gestation period for this problem.

The mean is 7.65 lbs and the standard deviation is 1.12 lb.

Week 6 Lab

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Birth Weights in America, Number 3, part b continued

Using the NORMINV function with the .9 (left to right) to find the point at which 90% of the values are below and 10% above, the mean, and the standard deviation. The distribution “fills” from left to right.

Week 6 Lab

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Birth Weights in America, Number 4, part b

We will identify the mean birth weight and standard deviation for the 37 to 39 week gestation period for this problem.

The mean is 7.33 lbs and the standard deviation is 1.09 lb.

Week 6 Lab

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Birth Weights in America, Number 4, part b continued

Using the NORMDIST function with the points in question, I subtracted the value for 6 from the value for 9. This was .9373 - .1112 which equals our answer .8261

Week 6 Lab

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Birth Weights in America, Number 5, part b

We will identify the mean birth weight and standard deviation for the 32 to 35 week gestation period for this problem.

The mean is 5.73 lbs and the standard deviation is 1.48 lb.

Week 6 Lab

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Birth Weights in America, Number 5, part b continued

Using the NORMDIST function with the point in question, the mean, the standard deviation, and the cumulative value “TRUE” gives the percent of babies under 3.3 lbs. The distribution “fills” from left to right.

Week 6 Lab

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Week 6 Lab

Part 2……….

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Age Distribution in the United States

Week 6 Lab

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Week 6 Lab

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Age Distribution in the United States, Number 1

The answer for number 1 is given to us. Make sure you see how it was calculated.

Week 6 Lab

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Age Distribution in the United States, Number 2

You will be finding the mean or average for the sample means in number 2. Use the Sample Means given in the lab’s Excel file.

Week 6 Lab

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Age Distribution in the United States, Number 3

Does this look like a “Bell-Shaped” curve to you?

Week 6 Lab

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Age Distribution in the United States, Number 4

On this one, use your same approach to creating a histogram that you did in a previous lab. You will use the sample data, set up your classes, find the frequencies, then create your histogram.

Does it look like a normal curve?????

Week 6 Lab

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Age Distribution in the United States, Number 5

The answer for number 5 is given to us. Make sure you see how it was calculated.

Week 6 Lab

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Age Distribution in the United States, Number 6

You will be finding the standard deviation for the sample means in number 2. Use the Sample Means given in the lab’s Excel file and compare to the Central Limit Theorem in your book. What does the Central Limit Theorem say? Discuss how it applies here.

Week 6 Lab

Part 3……….

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Finding z and t scores, Part 3

Week 6 Lab

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Week 6 Lab

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Finding z and t scores, Number 1b

Just input your value under Confidence level and the z-score is calculated for you! Make sure you look at the formula.

Week 6 Lab

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Finding z and t scores, Number 2b

Just input your value under Confidence level and sample size and the t-score is calculated for you! Make sure you look at the formula.

Week 6 Lab

Part 4……….

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Bob’s Candies (Using Confidence Intervals…), Part 4

Week 6 Lab

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Week 6 Lab

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Bob’s Candies, Number 1

Use the “average” function and the “stdev” function in Excel to find the sample mean and sample standard deviation.

Week 6 Lab

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Bob’s Candies, Number 2

In answering this question, take a look at the sample size!

Week 6 Lab

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Bob’s Candies, Number 3

Based on your answer for number 2, choose the appropriate values using the same Excel functions you used in Part 3 of the lab.

Week 6 Lab

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Bob’s Candies, Number 4

For 95% you would

Use the formula E=Zc*(s/sqrt n), which =1.96*(6.205/6.325)=1.923Then find your endpoints, the Left endpoint would be x-E=Mean -1.923=______

The Right endpoint would be x+E=Mean +1.923=____So, you can be 95% confident that the true mean amount the citizens spend per year is between ____and ______.

Week 6 Lab

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Bob’s Candies, Number 5

On this one I would take a look at say the 99% lower limit (left hand limit). Discuss this. You would do this the same way you did the previous question (Number 4).

Week 6 Lab

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Bob’s Candies, Number 6

On this question, compare Bob’s results (his data) to the national average ($75 per person).

Remember I will post the link to these charts at

www.facebook.com/statcave

Come to my facebook site throughout the week and I might post a few more hints.

Week 6 Lab