# MS 150 Statistics q10 9.2 • Name:

Number of
centerline reflectors
per half kilometer
84
74
78
61
67
55
54
62
61
83
81
75
70
65
70
76

The number of new orange centerline reflectors from the Sokeh's Island junction to the college in Palikir was counted by a three person team. The numbers are the number of markers for each half kilometer.

1. _________ Calculate the sample size n.
2. _________ Calculate the sample mean x.
3. _________ Calculate the sample standard deviation sx.
4. _________ What is the point estimate for the population mean μ?
5. _________ Calculate the standard error SE.
6. _________ Calculate the number of degrees of freedom.
7. _________ Calculate t-critical tc for a confidence level c of 95% (0.95)
8. _________ Calculate the margin of error E.
9. Calculate the 95% confidence interval for the population mean μ

p(__________ ≤ μ ≤ __________) = 0.95
Confidence interval statistics
Statistic or ParameterSymbolEquationsOpenOffice
Degrees of freedomdfn − 1 =COUNT(data)-1
Find a tcritical value from a confidence level c tc =TINV(1-c;df)
Standard error of the sample mean SE =STDEV(data)/SQRT(sample size n)
Calculate a margin of error for the mean E for n ≥ 5 using sx. E =tc*sx/SQRT(n)
Calculate a confidence interval for a population mean μ from a sample mean x and an error tolerance E x − E ≤ μ ≤ x + E