Answer:
D
Step-by-step explanation:
To find the rate of increase all you have to do is take one of the data sets to see that every two months its charge time increases by 15 minutes or 7.5 minutes every month.
Hope this helps sorry my writing is messy
Using it's concept, the standard deviation of the data is of 3.742.
<h3>What are the mean and the standard deviation of a data-set?</h3>
- The mean of a data-set is given by the <u>sum of all values in the data-set, divided by the number of values</u>.
- The standard deviation of a data-set is given by the square root of the <u>sum of the differences squared between each observation and the mean, divided by the number of values</u>.
For this data-set, the mean is:
M = (1 + 4 + 4 + 4 + 4 + 6 + 5)/7 = 4.
Hence the standard deviation is:

More can be learned about the standard deviation of a data-set at brainly.com/question/12180602
#SPJ1
Answer:
Standard deviation 46.3
Step-by-step explanation:
A 28% of the distribution is equivalent to a z score of -0.5828, you can use a z table to find that.
Z score is calculated as follows:

x is the number being evaluated
μ is the mean
σ is the standard deviation
And it is used to calculate how many standard deviations you are from the mean of the sample.
Replacing with the known information you can calculate the standard deviation:

1/4 divided by 6 equals:
0.0416666667
<span>Hope that helps and correct me if I'm wrong!</span>