Consider the population of electric usage per month for houses. The standard deviation of this population is 128 kilowatt-hours. What is the smallest sample size to provide a 90% confidence interval for the population mean with a margin of error of 30 or less

50

Step-by-step explanation:

Formula for sample size(n) if population standard deviation is known:

, E = Margin of error , =  Critical z-value

As per given,

kilowatt-hours.

Critical z-value for 90% confidence = 1.645

E =  30

Required sample size :

Hence,  the smallest sample size to provide a 90% confidence interval for the population mean with a margin of error of 30 or less = 50

answer: true

step-by-step explanation:

54 km / hours

step-by-step explanation:

we need to convert seconds to hours

60 seconds = 1 minutes

60 minutes = 1hour

15 m         60 second   60 minutes

  * *         = 54000 meters/ hour

second     1 minute             1 hour

now we need to convert meters to km

1000 m = 1 km

54000 m       1 km

*   = 54 km / hours

hour               1000m