# Formula for the Confidence interval?

#### khaled2reza

##### New Member
Formula for the Confidence interval, assuming for a Sample whose standard deviation is same as Population.

I need to know the exact formula. I need to know if there is any square root of n in the denominator. Anyone who knows the formula please share.

#### Dason

Estimate +/- (margin of error)

#### khaled2reza

##### New Member
What would be the solution to this problem attached?

#### khaled2reza

##### New Member
anyone knows the solution? I am having confusion at the assumption part.

#### rogojel

##### TS Contributor
Hi,
this is obviously a homework assignement: so, what do you think?

#### khaled2reza

##### New Member
Hi,
this is obviously a homework assignement: so, what do you think?
Hi,

I have the solution for this problem I dont understand the logic behind it. In the confidence interval formula, there is no root-n in the denominator. What is the reason?