The standard deviation for the lifetimes of lawn mowers is estimated to be 800 hours (for the entire population). We'd like to collect data and be 97% confident that our margin of error will not exceed 50 hours. What is the minimum sample size we would need to select, to achieve this

So the answer for this case would be n=1206 rounded up to the nearest integer

Step-by-step explanation:

We know the following info:

the standard deviation estimated7

The margin of error is given by this formula:

   (a)

And on this case we have that ME =50 and we are interested in order to find the value of n, if we solve n from equation (a) we got:

  (b)

The critical value for 97% of confidence interval and using a significance level of and , replacing into formula (5) we got:

So the answer for this case would be n=1206 rounded up to the nearest integer

The answer is the third choice: -1/4.
Here’s why: if you count from 0 to 1 or -1, it’s 4 steps. That means the fraction would have a denominator of 4, if there were 5 parts, then the denominator would be 5...and so on. The numerator is 1 because 0 to the point is 1 step. But now why negative? Because everything to the left of 0 on the number line will be negative, everything right of 0 on the number line will be positive.
Hope this also helped you to understand for future problems like this.