Which is the least expensive unit rate:
3 for $1.26
4 for $1.68
5 for $2.25

So 3 for $1.26 and 4 for $1.68

Step-by-step explanation:

3 for $1.26 means $0.42 per each

4 for $1.68 means $0.42 per each

5 for $2.25 means $0.45 per each

So 3 for $1.26 and 4 for $1.68 would be the least expensive unit rate!

Hope this help :3

The confidence interval for the mean is given by the following formula:

  (1)

Or equivalently:

For this case we have the interval given (3.9, 7.7) and we want to find the margin of error. Using the property of symmetry for a confidence interval we can estimate the margin of error with this formula:

Step-by-step explanation:

Previous concepts

A confidence interval is "a range of values that’s likely to include a population value with a certain degree of confidence. It is often expressed a % whereby a population means lies between an upper and lower interval".

The margin of error is the range of values below and above the sample statistic in a confidence interval.

Normal distribution, is a "probability distribution that is symmetric about the mean, showing that data near the mean are more frequent in occurrence than data far from the mean".

represent the sample mean for the sample  

population mean (variable of interest)

Solution to the problem

The confidence interval for the mean is given by the following formula:

  (1)

Or equivalently:

For this case we have the interval given (3.9, 7.7) and we want to find the margin of error. Using the property of symmetry for a confidence interval we can estimate the margin of error with this formula: