80 students from a school volunteered for the study. Half of them… Step by Step

Step by step

The question

Question: 80 students from a school volunteered for the study.

Half of them chose to use a study app.

The app group got better marks.

What can the study say?

1 Two questions

To judge a study, we ask two questions.

How were the students picked?

And how were the groups made?

2 How they were picked

The story says the students volunteered.

They chose to join.

So: no, not at random.

People who join by themselves can be different from the others.

volunteers: only people who wanted to

Careful!

A big group is not enough.

Volunteers may be different from the rest of the school.

Careful: not 80 students → true for everyone ✗

So what we find is true only for people like these, not for the whole school.

3 How the groups were made

The students chose for themselves.

So: no, not at random.

People who choose to use a study app may be different in other ways too.

they chose: the groups may differ in other ways

So the app and the better result go together.

But maybe the app did not cause it.

4 What the study can say

So the study can say: the app and the result go together, only for people like these.

Maybe the app is not the cause.

= linked, for people like these

5 Check

Let's check with the story.

The first sentence says: volunteered.

That matches.

"volunteered" → only people like these

The second sentence says: they chose.

That matches too.

So the answer is right!

"chose" → maybe not caused

Let's look back.

First: two questions.

Then: how they were picked.

Then: how the groups were made.

Then: what the study can say.

Last: check.

Answer