Marie works for an optician. She records the depth of a lens in each of the 100 pairs of glasses on display.
Depth
Her results are summarised in the table.
Number of pairs of glasses
Depth of lens, x mm,
to the nearest mm
10 << 20
5
20 < X < 30
20
30 < x < 40
23
40 <r< 50
52
In which group does the median lie?
(1 mark)
10 < x < 20
20 < x < 30
30 < x < 40
40 < x < 50​

false

step-by-step explanation:

85.560%

step-by-step explanation:

conditional probability is defined as:

p(a|b) = p(a∩b) / p(b)

in other words, the probability that a occurs, given that b has occurred = the probability that both a and b occur / the probability that b occurs.

in this example:

p(turns 64 | turns 44) = p(turns 64 & turns 44) / p(turns 44).

if someone turns 64, they must have already turned 44, so:

p(turns 64 | turns 44) = p(turns 64) / p(turns 44)

on page 42, we see that of the original 100,000, 94944 turn 44, and 81234 turn 64.   therefore:

p(turns 64 | turns 44) = 81234 / 94944

p(turns 64 | turns 44) = 0.85560