Description Usage Format Source References Examples

Study explores how physical handicaps affect people's perception of employment qualifications. Researchers prepared 5 videotaped job interviews using actors with a script designed to reflect an interview with an applicant of average qualifications. The 5 tapes differed only in that the applicant appeared with a different handicap in each one. Seventy undergraduate students were randomly assigned to view the tapes and rate the qualification of the applicant on a 0-10 point scale.

1 |

A data frame with 70 observations on the following 2 variables.

`Score`

is the score each student gave to the applicant

`Handicap`

is a factor variable with 5 levels—

`"None"`

,`"Amputee"`

,`"Crutches"`

,`"Hearing"`

and`"Wheelchair"`

Ramsey, F.L. and Schafer, D.W. (2002). *The Statistical Sleuth: A
Course in Methods of Data Analysis (2nd ed)*, Duxbury.

Cesare, S.J., Tannenbaum, R.J. and Dalessio, A. (1990). Interviewers'
Decisions Related to Applicant Handicap Type and Rater Empathy, *Human
Performance* **3**(3): 157–171.

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 | ```
str(case0601)
boxplot(Score~Handicap, data=case0601, ylab="Score")
aov.handicap <- aov(Score ~ Handicap, case0601)
summary(aov.handicap)
TukeyHSD(aov.handicap)
#Calculate confidence interval for linear combination
#(wheelchair+crutches)/2 - (amputee+hearing)/2 as in Display 6.4
mean.handicaps <- with(case0601, tapply(Score, Handicap, mean))
var.handicaps <- with(case0601, tapply(Score, Handicap, var))
n <- 14
s.pooled <- sqrt(sum((n-1)*var.handicaps)/sum((n-1)*5))
## either
cr.wh <- mean.handicaps["Wheelchair"] + mean.handicaps["Crutches"]
am.he <- mean.handicaps["Amputee"] + mean.handicaps["Hearing"]
g <- cr.wh/2 - am.he/2
## or
contr <- c(0, -1, 1, -1, 1)/2
g <- sum(contr * mean.handicaps)
se.g <- s.pooled * sqrt(sum(contr^2)/n)
t.65 <- qt(.975, 65)
## ci
g + c(-1,1) * t.65 * se.g
``` |

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