The eyesight of 7477 women aged 30 to 39 who were employed in Royal Ordnance factories was assessed. Each eye was graded separately on a scale from 1 (very good) to 4 (poor). The results are shown in the table below.
|
|
| left eye grade |
| total | ||
|
|
| 1 | 2 | 3 | 4 |
|
| right | 1 | 1520 | 266 | 124 | 66 | 1976 |
| eye | 2 | 234 | 1512 | 432 | 78 | 2256 |
| grade | 3 | 117 | 362 | 1772 | 205 | 2456 |
|
| 4 | 36 | 82 | 179 | 492 | 789 |
| total |
| 1907 | 2222 | 2507 | 841 | 7477 |
One woman is selected at random from these 7477 women.
What is the probability that this woman has grade 1 or 2 eyesight in both eyes?
What is the probability that this woman does not have grade 4 eyesight in her left eye?
+23246 The table is nearly impossible to read; also, I can't find a way for the numbers in the first row to sum to 1976.
Anyway:
What is the probability that a woman, selected at random, has grade 1 or 2 eyesight in both eyes?
-- Add up four numbers:
the number with grade 1 in left eye and grade 1 in right eye;
the number with grade 1 in left eye and grade 2 in right eye;
the number with grade 2 in left eye and grade 1 in right eye;
the number with grade 2 in left eye and grade 2 in right eye;
and divide this total by the total number of women.
What is the probability that this woman does not have grade 4 eyesight in her left eye?
-- Find the entry for grade 4 eyesight in her left eye; subtract this from the total number of women;
divide this answer by the total number of women.
