Question

How to calculate 95 confidence interval from standard deviation?

Answer 1

Answer:

Because you want a 95% confidence interval, your z*-value is 1.96.

Suppose you take a random sample of 100 fingerlings and determine that the average length is 7.5 inches; assume the population standard deviation is 2.3 inches. ...

Answer 2

Answer:

FIND ALL THE GIVEN FIRST BEFORE CALCULATING THE INTERVAL

Step-by-step explanation:

Step 1

1.

Given:

ns==510.37

The degrees of freedom is obtained as below:

df===n−151−150

From the Chi Square table, the left side critical value for chi square with 50 degrees of freedom is χ20.052,50=71.4202.

From the Chi Square table, the right side critical value for chi square with 50 degrees of freedom isχ21−0.052,50=32.3574.

Step 2

The 95% two-sided confidence interval for the standard deviation is obtained as below:

(n−1)s2χ2α2⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯√50×0.37271.4202⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯√0.3096<<<σ<(n−1)s2χ21−α2⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯√σ<50×0.37232.3574⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯√σ<0.4599

Thus, the 95% two-sided confidence interval for the standard deviation is (0.3096, 0.4599).