50 dogs were picked at random from a shelter. Half of them were… Step by Step

Step by step

The question

Question: 50 dogs were picked at random from a shelter.

Half of them were picked at random to get a new food.

The new food group gained more weight.

What can the study say?

1 Two questions

To judge a study, we ask two questions.

How were the dogs picked?

And how were the groups made?

2 How they were picked

The story says the dogs were chosen at random from the shelter.

So: yes.

At random means all the dogs in the shelter had the same chance to be picked.

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

random: all dogs in the shelter had the same chance

So what we find can be used for the whole shelter: true for all dogs in the shelter.

3 How the groups were made

The dogs were chosen at random to get a new food.

So: yes.

Chance made the groups, not the dogs.

So the two groups are alike, except for the new food.

random groups: alike, except for the new food

So the difference comes from the new food: the new food causes it.

Careful!

Only for the shelter they were picked from.

Not for all dogs everywhere.

Careful: not true for all dogs everywhere ✗

4 What the study can say

So the study can say: for all dogs in the shelter, the new food causes this.

= causes it, for the whole shelter

5 Check

Let's check with the story.

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

That matches.

"chosen at random from" → all the shelter

The second sentence says: chosen at random to get a new food.

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