A random sample of 40 college students has a mean earnings of $3120 over the summer months. Assume the population standard deviation of earnings over the summer months for college students is $677 and that the distribution of earnings over the summer months for college students is normally distributed. Determine whether a normal distribution or a t-distribution should be used or whether neither of these can be used to construct a confidence interval.

A normal distribution or z-test is used to construct a confidence interval.

Step-by-step explanation:

We are given the following in the question:

Sample mean, = $3120

Sample size, n = 40

Population standard deviation, σ = $677

The distribution of earnings of college is a normal distribution.

Conditions:

Conclusion:

Thus, we use a normal distribution or z-test to construct a confidence interval.

c.   x=2.4cm

step-by-step explanation:

similar triangles are triangles which have the same shape but not the same size. this means their angle measures are equal but their side lengths are not instead they are proportional. to solve, we will set up a proportion and solve.

a proportion is two equal ratios set equal to each other. we form the ratios by finding corresponding sides (sides which match to each other on both triangles by their position). out ratios will be one side of the small triangle over the corresponding side on the big triangle as shown below:

.

to solve the proportion, we'll cross multiply by multiplying numerator with denominator across the equal sign.