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Normal Distribution and Significance Level

Satisfactory Essays

Math 221
Week 6 Lab

Submitted by: Merima Ceric

Part 1. Normal Distributions and Birth Weights in America

1) What percent of the babies born with each gestation period have a low birth weight (under 5.5 pounds)? a) Under 28 = 99.88% The NORMDIST formula was used to calculate: =NORMDIST(5.5,1.88,1.99,True) X= 5.5 Mean= 1.88 Standard Deviation=1.19

b) 32 to 35 weeks = 43.83% The NORMDIST formula was used to calculate: =NORMDIST (5.5,5.73,1.48,True) X= 5.5 Mean= 5.73 Standard Deviation=1.48

c) 37 to 39 weeks = 4.66% The NORMDIST formula was used to calculate: =NORMDIST(5.5,7.33,1.09, True) X= 5.5 Mean= 7.33 …show more content…

3) No, the ages are not normally distributed because with the view of the histogram, it is not bell shaped.

4)

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Histogram is approximately bell shaped and symmetric and agrees with the results predicted by the Central Limit Theorem which says that whatever the population shape, the sampling distribution is approximately normal

5) Standard deviation = 3.5518 ( = STDEV formula was used) Standard deviation of population = 22.57 Standard deviation of sample mean=Standard deviation / sqauare root of sample size = 40 Therefore Standard deviation of sample mean= 3.567841 These two values are close; thus the result predicted by central limit theorem is true.

Part 3. Finding z- and t-scores for Confidence Intervals

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

a. 80%
Confidence level = 80% or Significance

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