Leslie is a biologist. She is going to randomly select one animal from her lab to study. There are 5
salamanders, 3 crayfish, and 12 minnows in her lab,
What is P(salamander)?

.25

Step-by-step explanation:

The probability that she selects a salamander is the number of salamanders(5), divided by all the animals she is going to choose from(20). 5 divided by 20 is equal to .25.

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