Answer:
Step-by-step explanation:
The formula for determining the confidence interval for the difference of two population means is expressed as
Confidence interval = (x1 - x2) ± z√(s²/n1 + s2²/n2)
Where
x1 = mean sale amount for mail order sales = 82.70
x2 = mean sale amount for internet sales = 66.9
s1 = sample standard deviation for mail order sales = 16.25
s2 = sample standard deviation for internet sales = 20.25
n1 = number of mail order sales = 17
n2 = number of internet sales = 10
For a 99% confidence interval, we would determine the z score from the t distribution table because the number of samples are small
Degree of freedom =
(n1 - 1) + (n2 - 1) = (17 - 1) + (10 - 1) = 25
z = 2.787
Margin of error =
z√(s²/n1 + s2²/n2) = 2.787√(16.25²/17 + 20.25²/10) = 20.956190
Easy!
Since the greatest multiple of 9 lesser than 79 is 72, you get a remainder of 7
8 7/9
The object should be placed 20/cm from the lens so as to form its real image on the screen
<h3>Mirror equation</h3>
The mirror equation is given according to the expression below;
1/f = 1/u + 1/v
where
f is the focal length
u is the object distance
v is the image distance
Given the following parameters
f = 5cm
v = 20cm
Required
object distance u
Substitute
1/5 = 1/u +1/20
1/u = 1/5-1/20
1/u = 3/20
u = 20/3 cm
Hence the object should be placed 20/cm from the lens so as to form its real image on the screen
Learn more on mirror equation here; brainly.com/question/27924393
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Answer:
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Step-by-step explanation:
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