Transcript Week 3 Lecture Statistics For Decision Making

B Heard
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 There are four parts to the lab this week:
 Part 1: Normal Distributions and Birth Weights in
America
 Part 2: Central Limit Theorem and Age Distributions
in the United States
 Part 3: Finding z and t scores for Confidence Intervals
 Part 4: Bob’s Candies (Using Confidence Intervals to
decide a course of action)
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Part 1……….
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 Birth Weights in America, Page 245
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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.
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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.
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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.
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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.
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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.
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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.
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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
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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.
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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.
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Part 2……….
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 Age Distribution in the United States, Page 277
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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.
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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.
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 Age Distribution in the United States, Number 3
Does this look like a
“Bell-Shaped” curve to
you?
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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?????
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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.
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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.
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Part 3……….
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 Finding z and t scores, Part 3
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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.
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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.
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Part 4……….
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 Bob’s Candies (Using Confidence Intervals…), Part 4
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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.
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 Bob’s Candies, Number 2
In answering this question, take a look at the sample
size!
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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.
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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)=1.923
Then 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 ______.
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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).
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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).
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S
STAT CAVE
See you next week:
“Same Stat Time, Same Stat Channel”
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I will post charts at:
4stats.wordpress.com