hypothesis testing(急, 20分!!)

(n - 1) s2 / sigma2 ~ Chi Square (degree of freedom = n - 1)
s = 12.2
sigma = 10
n = 15

c2 = (15 - 1) 12.22 / 102 = 20.8376
critical c2 for 10% significance level = 21.0641 > 20.8376
Hence, the distributor's claim is not correct.

p-value
Pr (c2 = 20.8376) = 10.5867%

2009-06-04 02:17:15 補充：
myisland8132 and hwqian are wrong

the question is not asking you to test the sample mean, but the standard deviation.

Hence, we should use Chi Square, but not Normal Distribution

2009-06-04 02:18:04 補充：
題目結構沒有問題

Ho : mean=10
H1: mean<10

整條題目結構有問題, 10 應是 population mean.
distributor's claim 應是 11.7, 12.2. 故H1 is mean > 10 較合理.

不論如何, 都可以計.
one tail test.
critical value 不是 1.282 嗎?
第一句的 s.d. , 我想是 mean 吧, 但 s 太大.
p-value = p(z < 0.5397)=0.7054, too large, not significant, accept Ho, claim is incorrect.

H0: The breaking strength of the thread is less than or equal to 10kg/cm2
H1: reject H0

Test-statistic
=sqrt(15)(11.7-10)/12.2
=0.5397

The critical value is 1.345

Conclusion: Do not reject H0 and conclude that the breaking strength of the thread is less than or equal to 10kg/cm2.

(ii) p-value=0.298942


2009-06-03 23:59:59 補充：
個standard deviation 有問題