The actual voltages of power packs labeled as 12 volts are as follows: 11.77, 11.90, 11.64, 11.84, 12.13, 11.99, and 11.77. The critical value for a 99% confidence interval for this sample is ________.
2007-06-25 08:21:29 · 4 answers · asked by Anonymous in Science & Mathematics ➔ Mathematics
You have 7 data points, n = 7.
Now if the population standard deviation is known (which is rarely the case), then you use the z statistic:
z_crit = 2.576
If the population std dev is not known, and you're using hte sample std dev as an estimator of the true std dev, then you have to use a t statistic, with degree of freedom n-1 = 6.
t_crit = 3.70743
**EDIT**
Yes Patrick is right, I've made the necessary corrections.
2007-06-25 08:34:08 · answer #1 · answered by Dr D 7 · 2⤊ 0⤋
There are only 6 degrees of freedom not 11
critical value = 3.70743
2007-06-25 08:45:13 · answer #2 · answered by walsh_patr 3 · 0⤊ 0⤋
What kind of test are you using? Are you using a T-test or a Z-score?
2007-06-25 08:23:48 · answer #3 · answered by JJ 2 · 0⤊ 0⤋
JJ is correct. Moreover, it is not clear exactly what is critical
2007-06-25 08:27:35 · answer #4 · answered by cattbarf 7 · 0⤊ 0⤋