Answer:
Option C is right
Step-by-step explanation:
Given are two samples
I group has sample size 90, mean = 9.2 and std dev =0,.37
II group has sample size 70, mean = 7.3 and std dev = 0.58
we find that mean difference i.e. difference between mean hours of sleep between two groups
= 9.2-7.3 = 1.9
Std error for difference = 0.0620
Since sample size is sufficiently large we can use Z critical for 99%
i.e. 2.58
Margin of error =±2.58(0.062)
=0.16
Hence confidence interval 99% for difference in hours of sleep
= (1.9-0.16,1.9+0.16)
=(1.74, 2.06)
you have to add 90 +90 3 times then theres your answer :)
We have been given that Sterre charges $35 to file tax returns, but files for free if she only needs the easiest form. Also, she donates $2 to clean water projects per tax return she files.
Further we know that Sterre charged $7,245 and made a donation of $1,242 this year for the tax returns she filed.
Let x be the number of free income tax returns and y be the number of $35 income tax returns.
Therefore, we can set up:

Since she donates $2 for each return that she files, therefore, we can set up:

Therefore,
Sterre filed 414 tax returns for free and filed 207 tax returns for $35.