Basics

Question 1

Valid conclusions

Answer 1

• Large sample size SO representative
• Long study SO can allow…. / see effect of X
• Control used SO comparison can be made.
• Mean & SD SO significant differences can be determined.

Question 2

Limitations:

You can only use the information provided.

Answer 2

• Small sample size, not representative;
• Only sampled males, females may respond differently to treatment;
• Only tested on …….. in a lab, in the wild, may obtain different pattern in data;
• Only tested on …….. species, might not be true for all species;
• No STATS test so differences could be due to chance;
• Data is SUBJECTIVE, some people may have lied.•

Question 3

Null hypothesis

Answer 3

• [x] will have no effect on [y]
• E.g. Temperature will have no effect on rate of reaction
• There will be no correlation between age and weight
• There will be no difference between the observed and expected ratio of 3:1 brown eyes to blue eyes

Question 4

The student did not draw a line of best fit.

Suggest two reasons why.

Answer 4

Not possible to predict intermediate values;

2. Only one result for each time period / not mean values;

Question 5

A student wanted to investigate the resting blink rate in people 60 years of age and people 15 years of age.

Describe how the student could find out whether there was a significant difference in blink rates between the two age groups.

Answer 5

Reference to large group size;

2. Reference to matching a specific, named variable;
3. Applying a statistical test to the data;
4. Accept ‘≥ 20 / many / lots’ but not ‘several / less than 20’
5. Accept any named variable other than age.
6. Accept ‘use SE / 95% confidence limits’

Question 6

The student did not carry out repeats. He was still able to carry out a statistical test.

Explain why.

Answer 6

Collected paired data;

Question 7

Explain the advantage of presenting the results as a ratio. 2

Answer 7

 1. Allows (valid) comparison;

2.      Number / sample size may vary;