Answer:
After 11 years the value of the investment reaches $1500.00
.
Step-by-step explanation:
The formula used for finding time (when the value reaches certain amount) is:
where A= Future VAlue
P= Principal Value
r= rate of interest (in decimal)
n= no of times investment is compounded
t= time
Putting the values given and finding Time t,
A= $1500
P= $1200
r= 2% or 0.02
n= 4 (compound quarterly)
Dividing both sides by 1200 and solving 0.02/4 = 0.005
Since t is in power we take the logarithm ln on both sides.
The rule of logarithm says that the exponent can be multiplied with the base when taking log
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
Answer:
16
Step-by-step explanation:
x=7-9
