Logit and probit

Currell: Scientific Data Analysis. Excel analysis for Fig 8.22 ukcatalogue.oup...
© Oxford University Press

[@thelma8760]

Dear Sir, Thank you for sharing your knwolodge!!!! ;) I don´t understand two things: 1) In 4min 27, when you calculate Corr,P you aply =ln (F5/(1-E5). Why E5? Isn´t ln(F5/(1-F5)? 2) Why did you use "five" (5) plus in Probit in the calculation? When I use logit and when I use Probit? Very very thanks!

[@slademeister]

+Thelma P. we add 5 so that the probit is in the middle with no zero values since you can't plot a zero on a log scale. e.g. No zero dose.

[@shivabhattarai1723]

+Slade Matthews Can we add numbers other than 5.

[@slademeister]

+Shiva Bhattarai We could if we wanted to shift the centre of the distribution. But this is not a standard use of probit.

[@jeffreygood8849]

Excellent video! Any advice for calculating 95% confidence intervals for the LC50 values obtained by this method?

[@kamakshaiah]

thanks for the video. very much useful. However, is it appropriate to predict for test value 5 for probit. I think probit is a special case of dichotomous dependent variable, where the responses must either 0 or 1 or 1, 2. Is it not?

[@ghulamalibaloch5241]

sir how we can draw this graph.. please explain .. thanks

[@slademeister]

I note that in calculating the logit you put the corrected probability of death over one minus the uncorrected P. Was this intentional? I feel that the odds should add up to one (outside of horse racing!! ). PS. An excellent video very clear indeed.

[@serviosilver9440]

Slade Matthews because it is approximately 4 times OLS

[@lizflorezp]

this video safe my life

[@alamreweyayu4977]

an excellent video! I learnt a lot from your video and thanks.

[@naveedkhan-pv4wc]

how the graph was formed

[@DaisyAleksa]

why we need to add 5 at probit?

[@outdoors0145]

This was done by Finney 1971 I believe and was due to the inverse normal distribution resulting in negative numbers below 0.5. Good video, additionally GLM can be used in R to do all this.

[@KashirVoice]

how the graph is draw in this videoif any one knows please tell

[@panjilove]

thank for the video analisis probit

[@messulanmeira6298]

thanks for the video, very useful