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

6 0

3 years ago

Pythagorean triples are given by the formulas x2 - y2, 2xy, and x2 + y2. Use the formulas for the Pythagorean triples to prove w

Arte-miy333 [17]

Let $k$ be an integer. Suppose there is a triangle with legs of length 16 and $2k+1$ . Then by the Pythagorean theorem, the length of the hypotenuse should be

$\sqrt{16^2+(2k+1)^2}=\sqrt{4k^2+4k+257}$

The formulas for Pythagorean triples say that if the legs are integers, then so must be the hypotenuse, because if $x=16$ and $y=2k+1$ are integers, then so are $x^2-y^2$ , $2xy$ , and $x^2+y^2$ .

However, $4k^2+4k+257$ is not a perfect square trinomial, which means for any integer $k$ , the length of the hypotenuse is not an integer, so such a triangle doesn't exist.

4 0

3 years ago

34 ft/min = ft/h please show example I want to know how to do it

Masteriza [31]

You know that there are 60 minutes in one hour, so you multiply 34 x 60.

4 0

3 years ago

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