Question

Noah gathered data at his school among 7th and 8th graders to see if there was an association between grade level and handedness. This table shows his data, but the number of right -handed 8th graders is missing .
Noah found there was no evidence of an association between grade level and handedness. Which of these could be the number of right-handed graders?

1)33
2)85
3)107
4)157

Answer 1

Answer: 4) 157

Step-by-step explanation:

We know that there is no association between the grade level and the andedness, then we should find that the ratio between left handeds and right handed is the same for both grades.

In 7-th grade we have:

Left handed : 11

Right handed: 72

The ratio is 11/72 = 0.14

Then, the ratio for the 8-th graders must be about the same:

Left handed: 24

Right handed: X

Ratio: 24/X

Let's start with the bigger option, X = 157.

24/157 = 0.15

Ok, we now see that with the bigger option we obtained almost the same ratio (if we use the smaller values for X, we will get a ratio bigger than 0.15, so 0.15 is the better aproximation that we can find to the 0.14 of the 7-th graders)

Then the correct option is 4) 157