I want to be able to record my students hopeful rise in test results.

What formula do I need for creating % rises in scores.

For example,

Johnny got 67 last time and 82 this time. How do I work out the % increase?

I want to be able to record my students hopeful rise in test results.

What formula do I need for creating % rises in scores.

For example,

Johnny got 67 last time and 82 this time. How do I work out the % increase?

the obvious way is just 82 - 67 = 15% increase.

otherwise, you could find the difference between them (15) and then divide by the initial score 15 / 67 = 22% increase on the original score…

But if the score’s not out of 100, you couldn’t do the subtract way, right?

And how come there are two different ways of doing it? Surely there is only one answer?

If Johnny got 100 out of 200, then 150 out of 200, his score has risen 25%.

So the formula is

```
last.score - first.score = x
x/total.possible.score x 100 = %increase
```

Thanks for that Teggs.

I can’t believe how crap I am at maths. Took me ages to figure out how to get a simple percentage for kids’ tests.

The formula is [(second_value - first_value)/(first-value)] x 100. So if Johnny got a 100/200 and 150/200 then the percentage change is

[(150/200 - 100/200)/(100/200)] x 100

= [(50/200)/(100/200)] x 100

= 50/100 x 100 {denominators cancel}

= 50% increase.

Think about it this way if Johnny gets a 100 and a 100 for both test scores then the net result is a 0% change. According to your formula it would be a 50% increase. Edit: Sorry that is not true.

Also note that if second value is smaller then the result is a negative percentage change.

So ow much have we improved in maths since the OP?

[quote=“teggs”]the obvious way is just 82 - 67 = 15% increase.

otherwise, you could find the difference between them (15) and then divide by the initial score 15 / 67 = 22% increase on the original score…[/quote]

The former is a “percentage point” increase, and the latter is a “percent” increase.

[quote=“Chris”][quote=“teggs”]the obvious way is just 82 - 67 = 15% increase.

otherwise, you could find the difference between them (15) and then divide by the initial score 15 / 67 = 22% increase on the original score…[/quote]

The former is a “percentage point” increase, and the latter is a “percent” increase.[/quote]Sorry, what on earth does that mean?

Is it important?

Am I likely to cause Johnny a severe beating due to my dog-eared maths knowledge?

I would tell Johnny he is improving, but that he still has a long way to go before I buy him a beer.

[quote=“wangdoodle”]Sorry, what on earth does that mean?

Is it important?[/quote]

Percentage point increase is like interest rates: “The Fed lifted interest rates 1%” means the base rate went from, say, 4% to 5%. However, the amount of interest you will pay on a loan actually increases by 25%.

It depends whether you want to measure improvement using a base of 100 (percentage point increase) or from a base of the score the student previously achieved (percentage increase).