DATA ANALYSIS II

1
DATA ANALYSIS II

• MKT 525

2
CROSS-TABULATIONS-1

• Numbers of Cars
• 1 or none 2 or more Total
• Income
• Less than 37,500 48 6 54
• or gt 37,500 27 19 46
• Total 75 25 100

3
CROSS-TABULATIONS-2

• Numbers of Cars
• 1 or none 2 or more Total
• Income
• Less than 37,500 89 11 100
• or gt 37,500 59 41 100

4
CROSS-TABULATIONS-3

• Numbers of Cars
• 1 or none 2 or more
• Income
• Less than 37,500 64 24
• or gt 37,500 36 76
• Total 100 100

5
CROSS-TABULATIONS-4

• Numbers of Cars
• 1 or none 2 or more Total
• Family size
• 4 or less 90 10 100
• 5 or more 23 77 100

6
CROSS-TABULATIONS-5

• Family 4 members or less 5 or more
• No. Cars 1 or none 2 or more 1 or
  none 2 or more
• Income
• Less than
• 37,500 96 4 50 50
• or gt
• 37,500 81 19 7 93

7
CROSS-TABULATIONS-6

• Size of family 4 or less 5 or more Total
• Income
• Less than 37,500 4 50 11
• or gt 37,500 19 93 41

8
Chi Square Test

• Does an observed set of frequencies match an
  expected pattern?
• Requirements
• samples in cells must be independent
• Expected frequency must be 5 or more
• SPSS Nonparametric- chisquare-test
  variable-expected value

9
(No Transcript)
10
Chi Square Compare Two Classifications
11
Compare means from two samplest-test

• Assume the 2 samples are independent
• Is there a difference in number of years to pay
  back a home improvement loan between SLs and
  other financial institutions?
• SL Other
• Mean years 8.7 7.7
• Variance .5 .6
• N 100 64
• t (8.7 - 7.7)/.1175 8.51
• At p.05, df n1n2-no. groups10064-2162,
  critical t 1.96

12
Compare proportions from two samples t-test

• Do younger women use bubble baths less than older
  women?
• Women under 35 Women 35-64
• p(use bb) .13 .23
• Std. Dev. .04 .04
• N 144 169
• Average p(use bb)weighted mean.184
• Std. error of diff. of proportions.0439
• t (.13 - .23) - 0 -2.28
• .0439
• df n - no. gps. 144 169 - 2 311 Critical
  t 1.96

13
SPSS

• Chi Square-compare two classifications
• Analyze-Descriptive Statistics -Crosstabs
  -Statistics-Chi square
• t-test -compare mean with expectation
• Analyze- Compare Means - One sample t-test - test
  variable - test value
• t-test - compare independent samples
• Analyze-Compare means -Independent samples-test
  variable-grouping variable-levels of 2 groups

14
Correlation

• Is there an association between two variables?
• If so, how strong is it?
• What is the form of the association?
• Correlation measure of relationship between two
  variables

15
Correlation-2

• CORRELATION DOES NOT MEAN CAUSATION!
• A measure of relationship NOT a proportion!
• Reflects a linear relationship.
• Can range from -1.00 to 1.00
• Correlation high if points close together when
  form a line and low if points are far apart when
  form a line.
• Correlation coefficient is standardized and
  dimensionless.
• Value of correlation degree of relationship
• Sign of correlation direction of relationship

16
SPSS for Correlation

• Both continuous
• Analyze-correlation-bivariate-enter 2 variables
• One dichotomous and one continuous
• Analyze-correlation-bivariate-enter 2 variables
• Both dichotomous
• Analyze-crosstabs-statistics-phi Cramers v
• Both ranks
• Analyze-correlation-Spearman-enter 2 variables

17
Simple linear regression

• Want to predict value of one variable (DV) from
  another variable (IV)
• Y bX a
• For each unit increase in X there is a b increase
  in Y
• r2 coefficient of determination proportion of
  variance accounted for by regression model.
• Relation between correlation coefficient (r) and
  b
• b r (s.d.y/s.d.x)

18
Simple regression SPSS

• Analyze- regression - linear - dependent variable
  name - independent (predictor) variable name

19
Case

• A baking company found a correlation of .70
  between the number of persons in a HH and the
  consumption of bread. They also found a
  correlation of -.35 between HH income and bread
  consumption.
• How would you interpret these findings?
• How much variance in HH bread consumption is
  explain by a linear regression model using the
  number of persons in the HH as the predictor
  variable?