I hope this helps you
square root of 441
square root of 21.21
square root of 21^2
21
Answer:

So we have at least 88.89% of the noise level values within 3 deviation from the mean.
Step-by-step explanation:
For this case let define the random variable X as the noise level, we know the following properties for X:

And for this case we don't know the distribution for the random variable X.
But we can use the Chebysev theorem who states that the minimum percentage of the data that lies within k standard deviations from the mean is given by:

So for this case we have that k = 3 and if we use this theorem we have:


And we can convert this into % and we got:

So we have at least 88.89% of the noise level values within 3 deviation from the mean.
The answer is negative two.
Answer: I think your answer is A. 1.8
Step-by-step explanation:
Not 100% sure but 90% though
<em>I HOPE THIS HELPS</em> sorry if its wrong
(7+4=11 white and red marbles) / (2+1+7+4=14 marbles in total) = 11/14