Question

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Entered Answer Preview Result 3.2498 3.2498 correct 3.94623 3.94623 incorrect At least one of the answers above is NOT correct. (1 point) A random sample of 10 size AA batteries for toys yield a mean of 3.84 hours with standard deviation, 1.2 hours. (a) Find the critical value, r*, for a 99% confidence interval.rº 3.2498 (b) Find the margin of error for a 99% confidence interval. 3.94623214 hour(s) Note: Round off your answer to 2 decimal places.

Answer 1

1)

sample mean 'x̄=	3.84
sample size   n=	10
sample std deviation s=	1.2
std error 'sx=s/√n=	0.3795
for 99% CI; and 9 df, value of t=		3.249835542
margin of error E=t*std error    =		1.23322588

2)

sample mean 'x̄=	103
sample size   n=	19
sample std deviation s=	12
std error 'sx=s/√n=	2.753
for 95% CI; and 18 df, value of t=		2.10092204
margin of error E=t*std error    =		5.78381486
lower bound=sample mean-E =		97.21618514
Upper bound=sample mean+E =		108.7838149
from above 95% confidence interval for population mean =(97.2162,108.7838)

3)

part1)

Standard Deviation, s: 1.7888543819998 Count, N 5 Sum, Ex: 674 Mean, X 134.8 Variance, s2: 3.2 Steps N 1 S = (xi – T), N 1 i=1 52- E(X; - x)2 N-1 (132 - 134.8)2 + ... + (135 - 134.8)2 5-1 12.8 4 = 3.2 S = 13.2 = 1.7888543819998

part 2)

X - tscorea * s/vn<u < X+ scorea * s/n where: X = sample mean, s = sample standard deviation, tscore = statistic with (n - 1) Degrees of Freedom and a = 1 - confidence Percentage

First find degrees of freedom: Degrees of Freedom = n - 1 Degrees of Freedom = 5-1 Degrees of Freedom = 4 Calculate a a = 1 - Confidence% a = 1 -0.95 a = 0.05 Find a spread range: a = 12(a) a = 72(0.05) a = 0.025 Find t-score for do.025 using 4 degrees of freedom: tscoreo.025 = 2.7765 <--- Value can be found on Excel using =TINV(0.05,4) tscore = 2.7765

134.8 - 2.7765 x 1.7888/5
to   
134.8 +2.7765 x 1.7888/15