Chris Graham

Chris Graham on Probability of the union of two non-mutually exclusive events 8 years, 5 months ago

Gave some feedback: Has some problems

Chris Graham commented on Probability of the union of two non-mutually exclusive events 8 years, 5 months ago

I think that the statement needs re-wording. As it stands, to me, it suggests that the people having "cereal and toast" are in addition to the others. I can't quite put my finger on it, perhaps the presence of "and"? Try this on Aiden and see what he thinks. 

In the advice, "The Venn diagram tells us..." is not required, as you have just created the Venn diagram from the info given. 

Chris Graham on Calculating Expected Values given a table of probabilities 8 years, 5 months ago

Gave some feedback: Has some problems

Chris Graham commented on Calculating Expected Values given a table of probabilities 8 years, 5 months ago

Can we invert the table so that "Film" and "P(Film)" are columns? Also, the table and everything above it should be the question's statement, with the part beginning "100 people..."

It's a nice straight-forward question, but you could add a little bit to this with an extra column "Genre", ie. action, comedy, sci fi etc. And then ask the student to calculate the expected number going to see a particular genre (of which there is say 2 films). Just make sure that you still have 'nice' numbers if you do this, so that the expected value comes to a whole number.

Chris Graham on Calculating expected values using theoretical probability and experimental probability 8 years, 5 months ago

Gave some feedback: Has some problems

Chris Graham commented on Calculating expected values using theoretical probability and experimental probability 8 years, 5 months ago

I was told that Alice rolled a die 350 times. I then find the expected number of rolls of a 3 or 5, which is 350/3, and am asked to round to the nearest integer. Why not make the number of rolls a multiple of 3 so that we get a round answer here?

Again in b) you could choose nice numbers. I got 297/350 which has no common factor, but 300/350 would have been lovely, and made part c) much more pleasant.

Chris Graham on Identify independent events 8 years, 5 months ago

Gave some feedback: Has some problems

Chris Graham commented on Identify independent events 8 years, 5 months ago

This looks good now. Just a couple of small changes to the advice:

• It doesn't make sense to number the parts of the advice in b), since they are not numbered in the question. Either number them (i),(ii),(iii), or find a different way to format the advice for b).
• The student does not need to work out the probabilities in order to answer the question, which is assessing their understanding of the concept. I would prefer that you draw your conclusion earlier in the advice for each part (e.g. for the cards, at the point where you state there are now only 51 cards in the deck, and only 3 kings) And then go on after that, with something like. "In fact, we can calculate...".

Chris Graham commented on Calculate the areas of polygons 8 years, 5 months ago

Aiden, is it just the conditional visibility which doesn't work? If so you could put 2 versions of the whole equation into different blocks: one for wh00 = wh00dp and one for wh00 <> wh00dp.