This problem is from the following book: goo.gl/t9pfIj We calculate areas on the standard normal curve and use areas to find cutoff values (z-scores). We do our calculations on a TI-84 Plus using the normalCDF & InvNorm functions.
Fellow Stats students, the Casio Fx-CG50 lets you input the "Tail" in a LEFT, RIGHT, or CENTRAL position into its Inverse Norm function, giving you BOTH left and right values in ONE computation - Ex: Tail: Central, Area: .7 Std Dev: 3.5 Mean: 200, Execute... "X1 Inv = 196.3724"; "X2 Inv = 203.6275 Highly recommended!
Some german student here. I've my final examination at school tomorrow and never fully understood the invNorm-command, but thanks to you I think that I now do
Great video! I'm studying for an exam and I've been going through youtube and I swear this was the most clear and helpful one. You also jumped straight into contend without any "hi my name is ___ and today we'll be...." which was super nice. Thanks for the help!
Can I also use normalcdf for the problem below? How can I find the answer using the TI-84 calculator? A company produces steel rods. The lengths of the steel rods are normally distributed with a mean of 218.7-cm and a standard deviation of 1-cm. For shipment, 6 steel rods are bundled together. Find the probability that the average length of a randomly selected bundle of steel rods is greater than 218.8-cm. P(M>218.8-cm)= Enter your answer as a number accurate to 4 decimal places. Answers obtained using exact z-scores or z-scores rounded to 3 decimal places are accepted.
Very nice video. What do you use normpdf for? I mean it practically gives the probability for a specific value (e.g. approximate a binomial distr. with a normal distr.) and you want to find out k=3, normpdf gives an approx. value but since the integral from 3 to 3 is zero, how can I interprete the result? Only as the density?
I grade AP Stats exams. You've got one major problem here: students need to know how much information to put down in order to get credit for work. If they draw a good picture, they'd probably be ok, but it would be GREAT for them to write instead: "normcdf(Left bound = 204, Right bound = infinity, mean = 200, SD = 3.5)" with the answer. Students need to label your "calculator speak" so the reader knows what the different numbers mean, and in your case the "work shown" (not counting the picture) would give the student an Incorrect. If students are really good with clear pictures, they can communicate the same info and be ok, but I find in grading these that students are inconsistent.
