Description Usage Value Note Author(s) References See Also Examples

Creates af binomial family object with the inverse link function equal to the psychometric function for the Two-Out-of-Five test.

1 | ```
twofive()
``` |

A binomial family object for models. Among other things it inludes the
psychometric function as
`linkinv`

and the inverse psychometric function (for direct
d-prime computation) as
`linkfun`

.

Several functions in this package makes use of functions in the twofive family object, but it may also be used on its own—see the example below.

Karolina Stachlewska

Ennis, J. M. (2013). A thurstonian analysis of the Two-Out-of-Five test. Journal of Sensory Studies, 28(4), pp. 297-310.

`duotrio`

, `triangle`

,
`twoAFC`

, `threeAFC`

,
`tetrad`

, `twofiveF`

,
`hexad`

, `discrim`

,
`discrimPwr`

, `discrimSim`

,
`AnotA`

, `discrimSS`

,
`samediff`

, `findcr`

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 27 28 | ```
## Estimating d-prime using glm for a Two-Out-of-Five test:
xt <- matrix(c(10, 5), ncol = 2) ## data: 10 correct answers, 5 incorrect
res <- glm(xt ~ 1, family = twofive)
summary(res)
## Equivalent to (Estimate and Std. Error):
discrim(10, 15, method="twofive")
## Extended example plotting the profile likelihood
## data: 10 correct answers, 9 incorrect
xt <- matrix(c(10, 9), ncol = 2)
summary(res <- glm(xt ~ 1, family = twofive))
N <- 100
dev <- double(N)
delta <- seq(1e-4, 3, length = N)
for(i in 1:N)
dev[i] <- glm(xt ~ -1 + offset(delta[i]),
family = twofive)$deviance
plot(delta, exp(-dev/2), type = "l",
xlab = expression(delta),
ylab = "Normalized Profile Likelihood")
## Add Normal approximation:
lines(delta, exp(-(delta - coef(res))^2 /
(2 * vcov(res))), lty = 2)
## Add confidence limits:
level <- c(0.95, 0.99)
lim <- sapply(level, function(x) exp(-qchisq(x, df=1)/2) )
abline(h = lim, col = "grey")
``` |

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