Identify is this is percent increase or percent decrease, then calculate percentage

Mathematics

1 answer:

vlabodo [156]3 years ago

3 0

Last year the chess club had 30 members. This year the club has 24 members.

Last year, the chess club had 30 members. This year, the club has 24 members. Since this year had less than last year ( 30 > 24), the percent will be decreasing.

To find the percent decrease, you have to use the following formula.

$\frac{Difference}{Original} \times 100$

Difference refers to the difference between the two numbers, 24 and 30. The difference between 24 and 30 is 6. Original refers to the original number, which is last year's amount of members in the chess group. Therefore, original = 30.

Substitute the numbers into the formula.

$\frac{Difference}{Original} =\frac{6}{30} =0.2$

To convert the decimal to a fraction, multiply the decimal by 100.

$0.2 \times 100 = 20 \%$

The answer is the number of chess members decreased by 20%.

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Since I started off by identifying whether it was decreasing or increasing, I did the work a bit differently. When finding the difference, you would usually subtract 30 from 24, which results in -6. Above I used 6, but if you used -6, you would end up with a result of -20%, which means it decreased by 20%. They bot end up with the same result, but you don't always have to first identify whether it's decreasing or increasing.

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You wish to compute the 99% confidence interval for the population proportion. How large a sample should you draw to ensure that

Nataly_w [17]

Answer:

$n=\frac{0.5(1-0.5)}{(\frac{0.13}{2.58})^2}=98.47$

And rounded up we have that n=99

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".

Solution to the problem

In order to find the critical value we need to take in count that we are finding the interval for a proportion, so on this case we need to use the z distribution. Since our interval is at 99% of confidence, our significance level would be given by $\alpha=1-0.99=0.01$ and $\alpha/2 =0.005$ . And the critical value would be given by: