80 is 40% of what number?

What is the y intercept of f(x)=(1/2)^x?

Varies inversely with x. if y=8.5 when x=-1 find x when y=-1

Now, martin can reasonably guess that the standard deviation for the entire population of people at the mall during the time of the survey is $1.50. what is the 95% confidence interval about the sample mean? interpret what this means in the context of the situation where 95 people were surveyed and the sample mean is $8. use the information in this resource to construct the confidence interval.