Answer:
b. Student-t with 48 degrees of freedom
Step-by-step explanation:
For this case we need to use a Two Sample t Test: equal variances.
Assumptions
When running a two-sample equal-variance t-test, the basic assumptions are "that the distributions of the two populations are normal, and that the variances of the two distributions are the same".
Let
and
be the sample means of two sets of data of size
and
respectively. We assume that the distribution's of x and y are:


Both are normally distributed but without the variance equal for both populations.
The system of hypothesis can be:
Null hypothesis: 
Alternative hypothesis: 
We can define the following random variable:

The random variable t is distributed
, with the degrees of freedom 
And the pooled variance can be founded with the following formula:

So on this case the best answer would be :
b. Student-t with 48 degrees of freedom
Answer:
Grace should use her phone for 58 minutes to maintain an average of 55 minutes.
Step-by-step explanation:
Usage of first month = 43 minutes
Second month = 62 minutes
Third Minutes = 57 minutes
Let, the usage of fourth month = k minutes
Mean of the data = 5 minutes
Now, Average of a Data = 
⇒
or, 55 x 4 = 162 + k
⇒ 220 - 162 = k
or, k = 58 minutes
So, Grace should use her phone for 58 minutes to maintain an average of 55 minutes.
The total length of the rope = 32 ft
It is cut into two sections, say x and y
But one section is seven times the other, say y=7x (shorter section being x)
Solving for x
x+y =32
x+7x = 32
8x=32
x=32/8 = 4 ft.
Therefore, the shorter piece is 4 ft long.
Simplest form would be, 5y-23+72 then it would be 5y+49
Answer:
Im not good at shapes and geometry but what i can tell u is that x = 1 so whenever u get ur area or whatever you can multiply it by one and thats what your answer is.
Step-by-step explanation: