180 children were chosen at random from a town. Half of them were… Step by Step

Step by step

The question

Question: 180 children were chosen at random from a town.

Half of them were chosen at random to play outside after school.

The outdoor play group slept longer.

What can the study say?

1 Two questions

To judge a study, we ask two questions.

How were the children picked?

And how were the groups made?

2 How they were picked

The story says the children were chosen at random from the town.

So: yes.

At random means all the children in the town had the same chance to be picked.

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

random: all children in the town had the same chance

So what we find can be used for the whole town: true for all children in the town.

3 How the groups were made

The children were chosen at random to play outside after school.

So: yes.

Chance made the groups, not the children.

So the two groups are alike, except for the outdoor play.

random groups: alike, except for the outdoor play

So the difference comes from the outdoor play: the outdoor play causes it.

Careful!

Only for the town they were picked from.

Not for all children everywhere.

Careful: not true for all children everywhere ✗

4 What the study can say

So the study can say: for all children in the town, the outdoor play causes this.

= causes it, for the whole town

5 Check

Let's check with the story.

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

That matches.

"chosen at random from" → all the town

The second sentence says: chosen at random to play outside after school.

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