Chris Graham

Chris Graham on Using Laws for Addition and Subtraction of Logarithms 8 years, 5 months ago

Gave some feedback: Has some problems

Chris Graham commented on Using Laws for Addition and Subtraction of Logarithms 8 years, 5 months ago

Part b) asks for the answers as a fraction, but the gaps do not accept fraction input. In addition, the correct answer is displayed as a decimal. Tick the "Allow the student to enter a fraction?" checkbox, which will also reveal an option to display the answer as a fraction.

In the advice, rather than (...), use \left( and \right) for parentheses, which scale to the height of the contents.

The pairs (i),(ii) and (iii),(iv) in part a) don't really ask anything different, but I think that's OK. You could have (iv) result in a fraction, though then you will need to add "Enter your answer as a fraction where appropriate" or similar in the part prompt.

Otherwise this is good.

Chris Graham commented on Find the equation of a line through two points - positive gradient 8 years, 5 months ago

One more. If I do not attempt the question, but reveal the answers, then the advice refers to an absent green line. This is another good reason to put the correct plot in the advice.

Chris Graham commented on Find the equation of a line through two points - positive gradient 8 years, 5 months ago

Similar points to our earlier discussion: 

This is a candidate for using the Numbas variables to set the jsxgraph axis limits. Move the block of code where you grab the Numbas variables in front of making the board, so that you have access to them. And then you can use them in the bounding box definition boundingBox:[yb-2,...] or whatever is sensible. Don't forget you'll want the intercept to be on the board.

Since you are only asking for the equation of the straight line through the points, you might consider creating a step with gapfills for the gradient and intercept, to allow the student to break the question down.

And you could add a second plot with the solution to the advice. 

One final thing: on one run I had B at the origin. You may wish to avoid this as it makes parts of the advice obsolete.

Chris Graham on Find the equation of a line through two points - positive gradient 8 years, 5 months ago

Gave some feedback: Has some problems

Chris Graham commented on Using the Quadratic Formula to Solve Equations of the Form $ax^2 +bx+c=0$ 8 years, 5 months ago

Nearly there!

In the steps you'll need to give the form of the quadratic equation associated with the solution, to assist the student in identifying $a$, $b$ and $c$.

Chris Graham on Using the Quadratic Formula to Solve Equations of the Form $ax^2 +bx+c=0$ 8 years, 5 months ago

Gave some feedback: Has some problems

Chris Graham on Which coin is more likely to be biased? 8 years, 5 months ago

Gave some feedback: Has some problems

Chris Graham commented on Which coin is more likely to be biased? 8 years, 5 months ago

I got 5 heads and 5 tails for the "distractor", which makes part a) very straightforward. I suggest that the imbalance in proportion of heads/tails is greater for coin 2 that coin 1, as it was when you put it up on the screen in the learning lab. 

I suggest the following changes to the wording:

• In the statement on the first line: "It is known that one of the coins is biased".
• Part a): "Based on the available results, ..." 

In the advice:

• "..., which would be the case for an unbiased coin". It is true in any case. The point being for an unbiased coin you would expect this to approach 0.5. You should explicitly state this. 
• "theoretical probability... should be..." it is a fact for an unbiased coin, no should about it.
• "is greater than 50%" would cover 70, 51, 50.00001. You probably don't want to get bogged down in compound probability calculations, but "signficantly different" would be an improvement. 
• Same with the "is greater than 50%" in part b).

Chris Graham on Probability - Notation and Conversion between Percentages, Decimals and Fractions 8 years, 5 months ago

Gave some feedback: Has some problems