Let's call our estimate x. It will be the average of n IQ scores. Our average won't usually exactly equal the mean 97. But if we repeated averages over different sets of tests, the mean of our estimate the average would be the same as the mean of a single test,
μ = 97
Variances add, so the standard deviations add in quadrature, like the Pythagorean Theorem in n dimensions. This means the standard deviation of the average x is
σ = 17/√n
We want to be 95% certain
97 - 5 ≤ x ≤ 97 + 5
By the 68-95-99.7 rule, 95% certain means within two standard deviations. That means we're 95% sure that
μ - 2σ ≤ x ≤ μ + 2σ
Comparing to what we want, that's means we have to solve
2σ = 5
2 (17/√n) = 5
√n = 2 (17/5)
n = (34/5)² = 46.24
We better round up.
Answer: We need a sample size of 47 to be 95% certain of being within 5 points of the mean
I can help you with #20. For example, lets say 3/5, this fraction would be made up of 5 parts and 3 are covered, which doesn't make it full, if it was 5/5 it would be full. When you do something with a reciprocal you turn it over, so 3/5 would be turned over to 5/3, thus making it a whole number
9514 1404 393
Answer:
C ≈ 0.00106455765168
Step-by-step explanation:
This is the sum of 13 terms of the geometric series that has 10000C/1.05 as the first term and a common ratio of 1/1.05. The sum S is given by ...
S = a1(1 -r^n)/(1 -r) . . . . a1 is the first term, r is the common ratio
Using the known values, we have ...
100 = (10000C/1.05)(1 -1.05^-13)/(1 -1/1.05))
0.01 = C(1 -1.05^-13)/0.05
C = 0.0005/(1 -1.05^-13) ≈ 0.0005/0.469679
C ≈ 0.00106455765168
Answer:
B
Step-by-step explanation:
