Question

In a certain population, 15% of the people have Rh-negative blood. A blood bank serving this
population receives 92 blood donors on a particular day.

a)What is the probability that more than 80 of the donors are Rh-negative?

someone please help. I get a z score of 0

Answer 1

I think you can use the binomial distribution, find \(P(x>80)=1-P(x\leq80)\)

Answer 2

ok. umm could you help with another question

Answer 3

i may be able to, may not though. post it

Answer 4

Suppose a random sample of n =25 observations is selected from a population that is normally
distributed, with mean equal to 106 and standard deviation equal to 12.

(a)Find the probability that the sample mean deviates from the population mean μ = 106 by no more than 4.

Answer 5

okay so find \(P(106\pm4)\)

\(z=\dfrac{110-106 }{12}=0.333\)

\(P(z=0.333)=0.1293\) (from a z-table)

because it's symmetric

=0.1293*2=0.2586

Answer 6

oh ok. thank you

Answer 7

I'm not entirely sure this is what they're asking for, what i did is basically the probability of sampling within \(\pm4\) of the mean.

But i think it's right

Answer 8

yeah.....it makes sense. thank you.

Answer 9

okay cool, no problem !

Answer 10

wait

Answer 11

how is the z score for 0.333 not 0.6293

Answer 12

The z-table i have gives values like this