There are 120 students in the seventh grade. Seventy percent of these students are involved in extracurricular activites. How ma
2 answers:
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Answer:
Critical value: z = 1.28
The 80% confidence interval for the mean repair cost for the washers is between $46.487 and $82.033.
Step-by-step explanation:
We have that to find our level, that is the subtraction of 1 by the confidence interval divided by 2. So:
Now, we have to find z in the Ztable as such z has a pvalue of
So it is z with a pvalue of 1-0.1 = 0.9, so z = 1.28
Now, find the margin of error M as such
In which is the standard deviation of the population and n is the size of the sample.
So
The lower end of the interval is the mean subtracted by M. So 64.26 - 17.773 = $46.487.
The upper end of the interval is M added to the mean. So 64.26 + 17.773 = $82.033.
The 80% confidence interval for the mean repair cost for the washers is between $46.487 and $82.033.
Answer:
a) x =3 and x=5
c) x =-1 and
i) x =0 and
Step-by-step explanation:
a)
Given that the quadratic equation
x² - 8x +15 =0
The factors of 15 = 5 × 3
x² - 5x -3x +15 =0
x(x -5) -3(x-5) =0
(x-3)(x-5) =0
x =3 and x=5
c)
3 x² + 10 x +7 =0
⇒ 3x² + 3x + 7x +7 =0
⇒ 3x (x +1) +7(x+1) =0
⇒ (x+1) ( 3 x +7) =0
⇒ x =-1 and
i)
2 x ² + 9 x =0
⇒ x( 2 x + 9) =0
⇒ x =0 and 2 x = -9
⇒ x =0 and