A-Level Maths: N2-03 Normal Distribution: Finding Probabilities Example 1

[bennybenson]

You've saved my A-level you absolute hero

[newton]

there's no point in thinking about what lower limit to use might as well just always pick -5000 or something

[academyzee]

You are a great teacher, thanks for your hardwork and commitment and keep posting

[samuelbarrfitness]

Currently a maths student at UoM and I'm still coming back to your videos in exam season!

[somtimesieat]

cheers mate got mymaths in for today big up james roberts for suggesting this video

[jayasharma]

How do you know when you have to use the z value?

[edanchan]

Hi, for question number 5, if we use normal PD, we can get a value that is equal to 0.09666… why the result will be different to the one that was calculated from normal CD function, which is zero?

[Pk_dilly]

Hi, for the first question, P(X<80), the first X value to show the probability of 0.5 is 55, but you went down until 40, would that change anything?

[ethanjohns]

for upper and lower limits just use either -10^99 (lower) or 10^99 (upper)

[AceOfHearts]

Markschemes tend to always show probablities from normal distributions getting derived using standard normal distribution. Whereas I understand once upon a time we had to use tables that had standard normal dist. prob, it is no longer the case, where we could now use a calculator. I wonder why questions dont specify use standard normal but yet expect pupils to use this long winded method where they reserve the marks.

[lindsayh-junm]

11:54 I found out from the table given by the book P(X>83) Z=0.75. The final answer is 0.7734, why did you subtract it from 1, sir?

[maddy]

hi, do we still need to learn Z values? i’ve been told its not a thing anymore and im really unsure..

[iampissed]

How do we calculate it on fx-991ES Casio calculator ?

[nmeo]

May I ask why you'd need to use the Standard Normal values/Z formula if you could just input the given values into the calculators to get the same result?

[newton]

can you get a less than or equal to inequality or would it just be the same as less than

[nathanlutala]

Great video! It's helped me to understand how to find probability using normal distribution. I have a question though: do you have to calculate the z value even though using the numbers in the question give the same answer?

[tzpzevu]

Hi sir, when do you actually have to use the standard normal distribution curve? Because at the moment it just seems the same as the other one

[jamjam]

Is using normal CD on the classwiz different to using binomial CD in that normal tells you <a and binomial tells you <=a?

[fahrenheit]

Your last point about picking a tree of exactly 81 metres is slightly inaccurate (at least in my opinion). While the probability of picking such a tree can only be 0, it is not impossible to pick one. If you say that a probability of 0 implies impossibility in this case, by that logic, since the probability of the height being any constant value is 0, it is impossible to pick a tree with any constant value of height, but this obviously cannot be the case, since any tree you pick will have a height that is some constant value (at least according to the model).

[panavvenigalla]

When i look at the z tables in the formula book for an answer for example for q 3 do I round 0.75 to the closest on the table to 0.8416? This gives me a p of 0.2 which is relatively close to 0.2266?