856 words - 4 pages

Math 221 **** Example Format ****

Week 6 Lab

Submitted by: (Insert Name)

Part 1. Normal Distributions and Birth Weights in America

1(a) 37 to 39 weeks as mean is around 7.33 lb.

1(b) 40 weeks as mean is around 7.72 lb.

1(c) 28 to 31 weeks as mean is 4.07 lb.

2(a) 99.88%, Excel command used was NORMDIST(5.5,1.88,1.19,TRUE).

2(b) 43.83%

2(c) 4.66%

2(d) 2.75%

3(a) Above 8.7269, Excel command used was NORMINV(0.9,7.33,1.09).

3(b) Above 9.0853

4(a) 41.41%, Excel command used was NORMDIST(9,5.73,1.48,TRUE)-NORMDIST(6,5.73,1.48,TRUE).

4(b) 82.61%

4(c) 81.56%

5(a) 88.36%, Excel command used was ...view middle of the document...

Finding z- and t-scores for Confidence Intervals

1. Using Excel, find the z-score that corresponds to the following Confidence Levels:

a. 80%

Answer: 1.282

b. 85%

Answer: 1.44

c. 92%

Answer: 1.751

d. 97%

Answer: 2.17

2. Using Excel, find the t-score that corresponds to the following Confidence Levels and Sample Sizes:

a. 95% with n = 25

Answer: 2.064

b. 96% with n = 15

Answer: 2.264

c. 97% with n = 21

Answer: 2.336

d. 91% with n = 10

Answer: 1.899

3. Suppose we wish to estimate the population mean using a confidence interval. When is it appropriate to use a z-score? When is it appropriate to use a t-score?

When our sample size is 30 or larger then distribution of sample means is normal

then we can use z-score.

When our sample size is less than 30 and we assume that the population is normal or approximately normal, if population standard deviation is unknown, we should use t-score but if population standard deviation is known we can use z-score.

Part 4. Bob’s Candies

1. Find the sample mean and sample standard deviation of the amount citizens spend per year.

Sample mean = 78.4

Sample standard deviation = 6.21

2. When finding a confidence interval for the true mean spent...

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