Which of these variables would MOST likely be examined through observational studies?

A) none of the variables
B) the economic output of a country
C) the speed at which a test object is released
D) the amount of current through an electric device

The number of chocolate chips in an 18-ounce bag of chocolate chip cookies is approximately normally distributed with a mean of 1252 chips and standard deviation 129 chips. (a) what is the probability that a randomly selected bag contains between 1100 and 1500 chocolate chips, inclusive? (b) what is the probability that a randomly selected bag contains fewer than 1125 chocolate chips? (c) what proportion of bags contains more than 1225 chocolate chips? (d) what is the percentile rank of a bag that contains 1425 chocolate chips?

Consider the graph of the exponential function y=3(2)×

Anyone? 15m is what percent of 60m; 3m; 30m; 1.5 km?