In: Statistics and Probability
Number of Pages Printed
2120 1953 2289 1897 2187 2283 2321 1956 2551 2423 2034 2221 2507 2110 2043 2476 2067 2119 1889 1734 2501 2333 2139 1998
Construct a 95% confidence interval to estimate the population mean of printable page numbers from the new printer and PLEASE interpret the result.
d) Repeat the same questions as (c) with 90% confidence level
Solution:
x | x2 |
2120 | 4494400 |
1953 | 3814209 |
2289 | 5239521 |
1897 | 3598609 |
2187 | 4782969 |
2283 | 5212089 |
2321 | 5387041 |
1956 | 3825936 |
2551 | 6507601 |
2423 | 5870929 |
2034 | 4137156 |
2221 | 4932841 |
2507 | 6285049 |
2110 | 4452100 |
2043 | 4173849 |
2476 | 6130576 |
2067 | 4272489 |
2119 | 4490161 |
1889 | 3568321 |
1734 | 3006756 |
2501 | 6255001 |
2333 | 5442889 |
2139 | 4575321 |
1998 | 3992004 |
∑x=52151 | ∑x2=114447817 |
a ) Mean ˉx=∑xn
=2120+1953+2289+1897+2187+2283+2321+1956+2551+2423+2034+2221+2507+2110+2043+2476+2067+2119+1889+1734+2501+2333+2139+1998/24
=52151/24
=2172.9583
b ) Sample Standard deviation S=√∑x2-(∑x)2nn-1
=√114447817-(52151)22423
=√114447817-113321950.041723
=√1125866.958323
=√48950.7373
=221.2481
Degrees of freedom = df = n - 1 = 24- 1 = 23
c ) At 95% confidence level the t is ,
= 1 - 95% = 1 - 0.95 = 0.05
/ 2 = 0.05 / 2 = 0.025
t /2,df = t0.025,23 =2.069
Margin of error = E = t/2,df * (s /n)
= 2.069 * (221.2 / 24)
= 93.4
Margin of error = 93.4
The 95% confidence interval estimate of the population mean is,
- E < < + E
2172.9 - 93.4 < < 2172.9 + 93.4
2079.5 < < 2266.3
(2079.5, 2266.3 )
d ) At 90% confidence level the z is ,
= 1 - 90% = 1 - 0.90 = 0.10
/ 2 = 0.10 / 2 = 0.05
t /2,df = t0.05,23 = 1.714
Margin of error = E = t/2,df * (s /n)
= 1.714 * (221.2 / 24)
= 77.3
Margin of error = 77.3
The 90% confidence interval estimate of the population mean is,
- E < < + E
2172.9 - 77.3 < < 2172.9 + 77.3
2095.5 < < 2250.3
(2079.5, 2266.3 )