12. Judith randomly selected 20% of the

Mathematics

2 answers:

kirill115 [55]3 years ago

7 0

Answer:

The answer is: C)200

Step-by-step explanation:

I took the test

Georgia [21]3 years ago

4 0

i believe the answer is 205

hope this helps

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The air pressure inside Jason’s bike tires decreases by about 6% each week. The original pressure was 45 pounds per square inch

Brrunno [24]

Compound percentage reduction can be calculated by multiplying the initial number by (1-x)^t where x is the percentage reduction (/100, i.e. 1% reduction is 0.01), and t is the number of times it has reduced.

So:
a) $p=45(1-0.06)^t=45*0.94^t$
Where t is the number of weeks.

We can then just substitute in to work out the final pressure:
b) p = 45*0.94^6 = 31psi

5 0

3 years ago

The proprietor of a boutique in New York wanted to determine the average age of his customers. A random sample of 25 customers r

jolli1 [7]

Answer:

$28-2.064\frac{10}{\sqrt{25}}=23.872$

$28+2.064\frac{10}{\sqrt{25}}=32.128$

So on this case the 95% confidence interval would be given by (23.9;32.1)

Step-by-step explanation:

Previous concepts

A confidence interval is "a range of values that’s likely to include a population value with a certain degree of confidence. It is often expressed a % whereby a population means lies between an upper and lower interval".

The margin of error is the range of values below and above the sample statistic in a confidence interval.

Normal distribution, is a "probability distribution that is symmetric about the mean, showing that data near the mean are more frequent in occurrence than data far from the mean".

$\bar X=28$ represent the sample mean

$\mu$ population mean (variable of interest)

s=10 represent the sample standard deviation

n=25 represent the sample size

Solution to the problem

The confidence interval for the mean is given by the following formula:

$\bar X \pm t_{\alpha/2}\frac{s}{\sqrt{n}}$ (1)

In order to calculate the critical value $t_{\alpha/2}$ we need to find first the degrees of freedom, given by:

$df=n-1=25-1=24$

Since the Confidence is 0.95 or 95%, the value of $\alpha=0.05$ and $\alpha/2 =0.025$ , and we can use excel, a calculator or a table to find the critical value. The excel command would be: "=-T.INV(0.025,24)".And we see that $t_{\alpha/2}=2.064$