500 voters were chosen at random from a state. Half of them were… Step by Step

Step by step

The question

Question: 500 voters were chosen at random from a state.

Half of them were chosen at random to read a short fact sheet.

The fact sheet group knew more.

What can the study say?

1 Two questions

To judge a study, we ask two questions.

How were the voters picked?

And how were the groups made?

2 How they were picked

The story says the voters were chosen at random from the state.

So: yes.

At random means all the voters in the state had the same chance to be picked.

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

random: all voters in the state had the same chance

So what we find can be used for the whole state: true for all voters in the state.

3 How the groups were made

The voters were chosen at random to read a short fact sheet.

So: yes.

Chance made the groups, not the voters.

So the two groups are alike, except for the fact sheet.

random groups: alike, except for the fact sheet

So the difference comes from the fact sheet: the fact sheet causes it.

Careful!

Only for the state they were picked from.

Not for all voters everywhere.

Careful: not true for all voters everywhere ✗

4 What the study can say

So the study can say: for all voters in the state, the fact sheet causes this.

= causes it, for the whole state

5 Check

Let's check with the story.

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

That matches.

"chosen at random from" → all the state

The second sentence says: chosen at random to read a short fact sheet.

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