Christian Lawson-Perfect

Christian Lawson-Perfect on Which coin is more likely to be biased? 8 years, 5 months ago

Gave some feedback: Has some problems

Christian Lawson-Perfect on Which coin is more likely to be biased? 8 years, 5 months ago

Saved a checkpoint:

I just don't know if there should be any marks for part a! If it was just a "what's your opinion" question, with no marks, then part b might challenge the student's intuition if they picked coin 2.

Working out experimental probabilities for the two coins as a first step might help - P(heads) would be higher for coin 2, but the point is that the sample size is small.

Or, the wording needs to be much more careful. Something like, "for which coin is there more evidence of bias?"

Christian Lawson-Perfect on Probability - Notation and Conversion between Percentages, Decimals and Fractions 8 years, 5 months ago

Gave some feedback: Ready to use

Christian Lawson-Perfect on Probability - Notation and Conversion between Percentages, Decimals and Fractions 8 years, 5 months ago

Saved a checkpoint:

Looks good!

The part that asks for a fraction also accepts a decimal, but that's a Numbas problem. I've got a long-standing issue on GitHub about acceptable answer formats: https://github.com/numbas/Numbas/issues/380 (this is for my reference only!)

Christian Lawson-Perfect on Use the factor theorem to identify factors of a polynomial 8 years, 5 months ago

Gave some feedback: Ready to use

Christian Lawson-Perfect on Use the factor theorem to identify factors of a polynomial 8 years, 5 months ago

Saved a checkpoint:

Looks good!

Christian Lawson-Perfect on Theoretical Probability vs Experimental Probability 8 years, 5 months ago

Gave some feedback: Has some problems

Christian Lawson-Perfect on Theoretical Probability vs Experimental Probability 8 years, 5 months ago

Saved a checkpoint:

The explanatory text that was in the statement should be at the top of the advice - I've moved it. 

The description of the experiment in the prompt for part a should be in the statement - it applies to every part.

I've changed "find the experimental probability of rolling a {number}" to "find the experimental probability of rolling a total of {number}".

I put the total number of trials in the statement - it's rare you'd do an experiment and not know how many times you did it, and adding up 11 numbers is a chore.

Lots of sentences in the advice start "therefore, ..." - try leaving it out, and if the sentence still makes sense leave it that way.

Is it important that the fractions are simplified? Do you need to explain how to do that in this question? I've taken away the "must be reduced" restriction, and I think the explanation of how to reduce a fraction in the advice can go.

"When two unbiased 6-sided dice are rolled together, the total shown on the faces has to be between 2 and 12. There are 36 possible outcomes when adding the faces of two dice together" is incorrect. There are 11 outcomes after adding. There are 36 outcomes when rolling two dice, one after the other. When two indistinguishable dice are thrown at the same time, you could make a case that there are 18 outcomes. This will trip students up, so it's important to be very clear.

Can you convince yourself that it doesn't matter if the dice are thrown one after the other or at the same time, if you're only looking at the total score? Can you rephrase the statement about the number of outcomes so that it's obvious?

I haven't got time to look at the last piece of advice, but it looks like there isn't any for part d. The table for part c should make it clear that this is just one sample, not the results you'd get every time.