60 plants were chosen at random from a farm. Half of them were… Step by Step

Step by step

The question

Question: 60 plants were chosen at random from a farm.

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

The plant food group grew taller.

What can the study say?

1 Two questions

To judge a study, we ask two questions.

How were the plants picked?

And how were the groups made?

2 How they were picked

The story says the plants were chosen at random from the farm.

So: yes.

At random means all the plants in the farm had the same chance to be picked.

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

random: all plants in the farm had the same chance

So what we find can be used for the whole farm: true for all plants in the farm.

3 How the groups were made

The plants were chosen at random to get a new plant food.

So: yes.

Chance made the groups, not the plants.

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

random groups: alike, except for the plant food

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

Careful!

Only for the farm they were picked from.

Not for all plants everywhere.

Careful: not true for all plants everywhere ✗

4 What the study can say

So the study can say: for all plants in the farm, the plant food causes this.

= causes it, for the whole farm

5 Check

Let's check with the story.

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

That matches.

"chosen at random from" → all the farm

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