Stats

Question 1

What is meant by standard deviation?

Answer 1

A measure of the spread of data around the mean value. It gives a better idea of the range of values.

Question 2

Overlap in standard deviations means

Answer 2

difference between means is insignificant

Question 3

Uncertainty of a measuring instrument is

Answer 3

plus/minus half the resolution of the instrument

Question 4

What is a reading?

Answer 4

A value found from an instrument using a single human judgement

Question 5

What is a measurement?

Answer 5

A value taken using two judgements, leaving two uncertainties, e.g. using a ruler

Question 6

Percentage uncertainty equation

Answer 6

(absolute uncertainty / value) x 100

Question 7

Uncertainty of the mean =

Answer 7

plus/minus half the range of the measured values

Question 8

When adding values…

Answer 8

Add the absolute uncertainties together

Question 9

If multiplying/dividing values…

Answer 9

Add percentage uncertainties together

Question 10

When using indices with a value…

Answer 10

Multiply the percentage uncertainty by the power

Question 11

What does log(4834928) =6.684 tell us

Answer 11

That 10 to the power of 6.684 = 4834928

Question 12

Percentage difference =

Answer 12

(difference / starting value) x100

Question 13

A statistical test was used to assess the effectiveness of five different vaccines in protecting against the flu. What would be the null hypothesis?

Answer 13

There is no significant difference between the type of vaccine and the number of people who contracted the flu

Question 14

Degrees of freedom for students t-test

Answer 14

(sample size of 1 - sample size of 2) - 2 or (n1 - n2) - 2

Question 15

If the t value is greater than or equal to the value for p = 0.05

Answer 15

The probability that the difference between means is due to chance is less than 5% and we can reject the null hypothesis

Question 16

If the t value is less than or equal to the value for p = 0.05

Answer 16

The probability that the difference between means is due to chance is greater than 5% and we can accept the null hypothesis

Question 17

How would you carry out a statistical test to determine whether the difference between means is significant (6)?

Answer 17

1. Construct a null hypothesis
2. Carry out a student’s t-test to compare means
3. Calculate the degrees of freedom for your t value
4. Use a critical value table to show p is less than or equal to 0.05
5. Compare your calculated t value against a critical value table.
6. If your t value is greater than or equal to the value on the critical value table, you can reject the null hypothesis