# Combining mean and standard deviation: mean score on AP Biology exam was 3.10...

#### Janeelise

##### New member
On an AP Statistics quiz I got this question and I have no clue how to solve it because it was never taught. I looked online for help but nothing has gotten me to the correct answe

In 2016, the mean score on the AP Biology exam was 3.10, with a standard deviation of 1.05. The mean score on the AP US History exam was a 2.74, with a standard deviation of 1.42. What is the combined mean and standard deviation for these exams?”

#### tkhunny

##### Moderator
Staff member
On an AP Statistics quiz I got this question and I have no clue how to solve it because it was never taught. I looked online for help but nothing has gotten me to the correct answe

In 2016, the mean score on the AP Biology exam was 3.10, with a standard deviation of 1.05. The mean score on the AP US History exam was a 2.74, with a standard deviation of 1.42. What is the combined mean and standard deviation for these exams?”

You should have been shown, or somehow discovered along the way...

2) Variance is additive. <== What does this suggest concerning the combining of the Standard Deviations?

#### j-astron

##### Junior Member
You should have been shown, or somehow discovered along the way...

2) Variance is additive. <== What does this suggest concerning the combining of the Standard Deviations?
Everything you said is true, and helpful hints for answering this question. I'm just wondering though: the question isn't asking for a sum of the two scores, with a variance for the sum. It's asking for a mean of the two scores, right? (Like, AP exam scores are out of 5). So doesn't that mean the OP needs to compute the mean of the means, and the error in that mean?

#### Janeelise

##### New member
You should have been shown, or somehow discovered along the way...

2) Variance is additive. <== What does this suggest concerning the combining of the Standard Deviations?

I tried just adding them, and it said I got it wrong.

#### stapel

##### Super Moderator
Staff member
I tried just adding them, and it said I got it wrong.
What numbers did you add? What result did you obtain? What is the "it" that said your value was incorrect? What value did it provide?

Thank you!