The answer to your problem would be 0.05
You need to find "two-fifths of 30." Of here means multiplication:
![\begin{aligned}\dfrac{2}{5}\cdot 30 &= \dfrac{2}{5}\cdot\dfrac{30}{1}\\[0.5em] &= \dfrac{60}{5}\\[0.5em] &= 12\end{aligned}](https://tex.z-dn.net/?f=%5Cbegin%7Baligned%7D%5Cdfrac%7B2%7D%7B5%7D%5Ccdot%2030%20%26%3D%20%5Cdfrac%7B2%7D%7B5%7D%5Ccdot%5Cdfrac%7B30%7D%7B1%7D%5C%5C%5B0.5em%5D%20%26%3D%20%5Cdfrac%7B60%7D%7B5%7D%5C%5C%5B0.5em%5D%20%26%3D%2012%5Cend%7Baligned%7D)
There are 12 athletes in the club.
Answer:
within ±1.96 standard deviations of the sample mean
Step-by-step explanation:
A 95% confidence interval is found using the formula C = 1 - α, and some other stuff, but let's focus on that for now. Using the formula:
.95 = 1 - α
α = .05
If α = .05, that means a 2-sided confidence interval would be found using the sample mean and the Z-score Z(subscript α/2), or Z.₀₂₅ because α AKA .05 divided by 2 = .025. From there, you take this either to your calculator or a Z-table (or perhaps you have a chart that lists the common CI values), and see that for the area to be .025 beneath a standard normal curve, your Z value is ±1.96 ("plus or minus" because we're considering a 2-sided confidence interval).
