100 students were chosen at random from a school. Half of them were… Step by Step

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The question

Question: 100 students were chosen at random from a school.

Half of them were chosen at random to use a math 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 were chosen at random from the school.

So: yes.

At random means all the students in the school had the same chance to be picked.

So the group is a fair small copy of the whole school.

random: all students in the school had the same chance

So what we find can be used for the whole school: true for all students in the school.

3 How the groups were made

The students were chosen at random to use a math app.

So: yes.

Chance made the groups, not the students.

So the two groups are alike, except for the app.

random groups: alike, except for the app

So the difference comes from the app: the app causes it.

Careful!

Only for the school they were picked from.

Not for all students everywhere.

Careful: not true for all students everywhere ✗

4 What the study can say

So the study can say: for all students in the school, the app causes this.

= causes it, for the whole school

5 Check

Let's check with the story.

The first sentence says: chosen at random from the school.

That matches.

"chosen at random from" → all the school

The second sentence says: chosen at random to use a math app.

That matches too.

So the answer is right!

"chosen at random to" → causes

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