In: Math
You will be performing an analysis on female heights, given of set of 30 heights that were randomly obtained. For this project, it is necessary to know that the average height for women is assumed to be 65 inches with a standard deviation of 3.5 inches. You will use these numbers in some of your calculations.
a. As you know, a random sample of 30 women’s heights was
obtained. Describe the sampling distribution. Use a full sentence
here to describe the sampling distribution. HINT: See the Chapter 8
Lecture Notes Key or the Chapter 8 video lecture if you are stuck.
You will not use the raw data yet.
b. In StatCrunch or Excel, find and state the mean of the 30
women’s heights that were provided (round to two decimal places).
Then (using the values from step 3), calculate the probability that
a random sample of 30 women’s heights would result in a mean that
was the value you found or more. Use this probability in a full
sentence.
c. For this step, please work under the assumption that we do not
know the population mean and standard deviation (and in fact, if we
are running this test, it means that we are not sure of these
values). Construct a 95% confidence interval for the average height
of a female. Interpret this confidence interval. HINT: You can use
the “with data” option
Height (in Inches) | Name |
72.44 | Emma |
67.53 | Olivia |
66.71 | Ava |
62.02 | Isabella |
73.89 | Sophia |
65.95 | Mia |
65.83 | Charlotte |
64.15 | Amelia |
65.39 | Evelyn |
59.68 | Abigail |
64.24 | Harper |
66.60 | Emily |
65.40 | Elizabeth |
64.72 | Avery |
67.11 | Sofia |
61.97 | Ella |
62.83 | Madison |
67.20 | Scarlett |
66.62 | Victoria |
68.78 | Aria |
66.13 | Grace |
64.47 | Chloe |
66.64 | Camila |
62.39 | Penelope |
63.90 | Riley |
62.97 | Layla |
59.31 | Lillian |
66.14 | Nora |
67.54 | Zoey |
63.45 | Mila |
a) sampling distribution-
µx = 65
σx = σ/√n = 3.5/√30 = 0.6390
b) Sample Mean, x̅ = ΣX/n = 65.4000
Z- score= (x̅ - µ )/SE = ( 65.400
- 65 ) / 0.6390
= 0.626
P( x̅ > 65.4) = P(z>0.626) = 0.2657
the probability that a random sample of 30 women’s heights would result in a mean that was 65.4 or more = 0.2657
c)
sample std dev , s = √(Σ(X- x̅ )²/(n-1) )
= 3.1125
Sample Size , n = 30
Sample Mean, x̅ = ΣX/n =
65.4000
Level of Significance , α =
0.05
degree of freedom= DF=n-1= 29
't value=' tα/2= 2.045 [Excel
formula =t.inv(α/2,df) ]
Standard Error , SE = s/√n = 3.1125 /
√ 30 = 0.5683
margin of error , E=t*SE = 2.0452
* 0.5683 = 1.1622
confidence interval is
Interval Lower Limit = x̅ - E = 65.40
- 1.162244 = 64.2378
Interval Upper Limit = x̅ + E = 65.40
- 1.162244 = 66.5622
95% confidence interval is (
64.24 < µ < 66.56
)