Hurricane frequencies The National Hurricane Center provides data that list the numbers of large (category 3, 4, or 5) hurricanes that have struck the United States, by decade since 1851 (www.nhc.noaa.gov/dcmi.shtml). The data are summarized below. Recently, theres been some concern that perhaps the number of large hurricanes has been increasing. The natural null hypothesis would be that the frequency of such hurricanes has remained constant. a) With 96 large hurricanes observed over the 16 periods, what are the expected value(s) for each cell? b) What kind of chi-square test would be appropriate? c) State the null and alternative hypotheses. d) How many degrees of freedom are there? e) The value of x2 is 12.67. Whats the P-value? f) State your conclusion.

STAT 110: Notes for Week of 9/13/16 Chapter 10 o In order to describe data, you must figure out if it is quantitative or categorical. o Quantitative Variable: a variable that measures something already in numerical form, ex. inches of a piece of paper, weight of a person, IQ, etc. o Categorical Variable: measures something that needs to be put into categories and/or given numerical value, ex. favorite color, ethnicity, current feelings, etc. o Distribution of a variable: tells what values of a variable occur and how often they occur, ex. 20 people like the color blue, 0 people like the color orange, etc. Distributions can be described through tables, graphs, or num