Question

Please ASAP

a) in a certain town live 780 families. A survey of 23 of them indicated that its average annual income is 80000 pesos, with a standard deviation of 3200 pesos. Located a 95% confidence interval for the average annual income of the entire population.

b) Eight families numbered from 1 to 8 are mixed in a container. If we extract two cards (no replenishment), what is the probability that the sum of their numbers is 9?

Thanks

Answer 1

a)

Here we have

Since

So it is not necessary to apply the finite population correction factor.

b)

Possible number of ways we can draw two cards without replacement is

Following table shows the two cards that can be draw without replacement to get sum 9:

Cards
1	8
2	7
3	6
4	5

That is out of 28 possible outcomes 4 shows sum 9 so the  probability that the sum of their numbers is 9 is

P(Sum 9) = 4 / 28 = 01429