The following data represents the age (in weeks) at which babies first

Ernest Ryland

Ernest Ryland

Answered question

2021-12-07

The following data represents the age (in weeks) at which babies first crawl based on a survey of 12 mothers conducted by Essential Baby:
- 52
- 30
- 44
- 35
- 47
- 37
- 56
- 26
- 39
- 26
- 39
- 28
a. Find the mean of the sample.
b. Find the standard deviation of the sample.
c. Construct a 95% Confidence Interval estimate for the mean age at which a baby first crawls. (Assume the data comes from a normal distribution.)

Answer & Explanation

Steve Hirano

Steve Hirano

Beginner2021-12-08Added 34 answers

a) x=xn =45912 
x=38.25 


b) s=1N1i=1N(xix)2, 
s2=(xix)2N1 =(5238.25)2++(2838.25)2121 =1100.2511 =100.02272727273 
s=100.02272727273 =10.001136299078 
s=10.0011 

c) n=12 
df=n1=11 
α=0.05 
tcritical value is tc=2.201 
E=tcsn =2.20110.001112 
E=6.35 


The 95% Cl is 
x±E =38.25±6.35 =(31.9,44.6)

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