Answer Sheet: Analysing ratio data

  1. UCS (star jumps) leads to UCR (increase in heart rate) (2)
  2. NS (duck quacking) plus UCS (star jumps) leads to UCR (increase in heart rate) (3)
  3. CS (duck quacking) leads to CR (increase in heart rate) (2)

Always follow instructions as to whether to round answers up. These answers have been rounded to 2 decimal places. (The table below was out of 4)

Before classical conditioning

To the Neutral Stimulus (duck quack)

After classical conditioning

To the Conditioned Stimulus (duck quack) (following ten pairings of quacking followed by 1 minute of star jumps)




Standard deviation  




Explain how and why Mrs Fake-Date would use the standard deviation? (3)

The standard deviation is a good measure of dispersion for Ms Fake-Data to use because it will allow her to understand more about how the data points in each condition are spread around the mean, for example are they closely packed around the mean (small standard deviation) or more variable (larger standard deviation).

She can use the SD because she has ratio level data in that she has collected heart rate in beats per minute (standardized units with a true zero).

Furthermore, it is a better measure for her to use than the range as every data point is used in the calculation and therefore it gives a more accurate and meaningful information about the dispersion of the scores. 

What can you conclude from your calculations? (2)

From these figures it would appear that the participants did become classically conditioned to the sound of the duck quacking because their mean heart rate was higher (112.63) after the pairing the of the duck quacking with the star jumping than it was before the pairings (96.63), a difference of 16 bpm, which equates to a 17% increase (16/96.63 x 100).

From the standard deviations it can be concluded that the spread of scores in both conditions was very similar as the SDs are only 1.7 bpm different to each other.