Casio STAT 2 Manuel d'utilisateur télécharger pdf (Page 57)

Activity 11

Exit Polls

Topic Area: Hypothesis Tests—Chi-square, Two-way Tables

NCTM Standards:

• Develop and evaluate inferences and predictions that are based on data

• Use simulations to explore the variability of sample statistics from a

known population and to construct sampling distributions (9-12)

• Understand how sample statistics reflect the values of population

parameters and use sampling distributions as the basis for informal

inference (9-12)

Objective

The students will be able to support or reject a null hypothesis based on given

data and calculations of confidence using a Chi-square distribution.

Introduction

The Chi-squared test is used to figure out if the rows of a set of data are contin-

gent upon the columns in that same set of data, or a test of independence. In this

activity, the students are presented with a set of "exit poll" data showing the num-

ber of votes for three different candidates at the sophomore, junior, and senior

level. The data was taken by a random poll of students after the vote. The null

hypothesis in this case states that the class level is independent of the candidate

voted for. If this null hypothesis is rejected, the students could say that there was

a difference in candidate preference between the three classes of students.

Use the following descriptions to go through the chi-square test manually:

In order to calculate the chi-square test, the student needs to calculate the row

and column totals and calculate the expected cell frequencies using the equation:

where E

cell1,A

is the expected frequency for the cell in the first column and the

first row,

T is the total number in the row or column, and N is the total number

in the entire table.

Teaching Notes

cell1,A

– T

(30.449)

(35.986)

(33.564)

100

(31.058)

(36.705)

(34.235)

102

(26.491)

(31.307)

(29.2)

104

289

Candidate 1 Candidate 2 Candidate 3 Total

Sophomore

Junior

Senior

Total

1 2 ... 52 53 54 55 56 57 58 59 60 61 62 ... 96 97

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Casio STAT 2 Manuel d'utilisateur Page 57

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