Program to Decrease Littering in California

A program to decrease littering was carried out in four cities in California’s Central Valley starting in August 2000. The amount of litter in the streets (average pounds of litter collected per block per day) was measured during the July before the program was started and then the next July, after the program had been in effect for a year. The results were as follows: Using the 1% level of significance, was there a significant decrease in the amount of litter? (a) Go through the five steps of hypothesis testing. (b) Illustrate your answer with a histogram of the sample’s difference scores and sketches of the population distribution (of difference scores) and the distribution of means (of difference scores), showing the t score and cutoff points for significance. c) Explain your answer to someone who understands mean, standard deviation, and variance, but knows nothing else about statistics.