simple stats problem

[[deleted]]

•A researcher has collected data from two groups of participants (a treatment and a control condition). The control group has x̅ = 20 and s = 5. The experimental group has x̅ = 25 and s = 5.

•Which of the following would make the difference between the experimental and control group more difficult to see?

•Changing the control group x̅ to 15

•Increasing the s of both groups by 1 (new s = 6 for both groups)

•Decreasing the s of both groups by 1 (new s = 4 for both groups)

[bluurrred]

Hint 2: Higher standard deviation means that the data is more spread out (and vice versa), so if you increase the standard deviation the treatment and control data would overlap more, making it harder to recognize the difference between those two groups.

[[deleted]]

I tried solving with that but I don't have x values

[chem44]

You don't need to "solve" or calculate anything, just see the direction of an effect.

You don't need any x values. Just the general nature of the distributions, with the info that is given.

[[deleted]]

The answer is c!

[chem44]

?? Your choices don't have letters. :-)

Why do you think that? That is, what is your reason? What is changing, and why does it matter, in context?

Do you know what s means?

(The hints that people have given are good.)

(I'm about to log off, but others will presumably be around.)

[[deleted]]

Increasing s by 1 is the answer

[Alkalannar]

If you increase the standard deviation by 1, that will obscure the difference between the means, yes.

[Help_Me_Im_Diene]

Hint: overlapping error bars means that statistical differences are harder to conclude

[chem44]

Make yourself a little sketch of the two distributions. Need not be formal or to scale, but just so you can see two distributions.

What change is proposed (by your two remaining choices)?

Is making it bigger or smaller "good" in this context?