How Science Works

Question 1

What does standard deviation show?

Answer 1

Spread of data around a mean and effect of any outliers

Question 2

Why should you use standard deviation bars are not ranges

Answer 2

1. Allows us to see the spread of data around a mean
2. Allows us to see effect of any outlines.

Question 3

What can scientist do to make this more reliable?

Answer 3

1. Repeat
2. Stats test to see if significant differences are due to chance
3. Peer review

Question 4

Valid conclusions need to be….

Answer 4

1. Large sample size so representative
2. Control used to see the effect of…
3. Mean and SD to determine significant differences

Question 5

Null hypothesis

Answer 5

X will have no effect if on the rate of reaction of y therefore
There will be no significant between mean rates of reaction

Question 6

Explain why a log scale is used

Answer 6

Large range in numbers and allows us to see exponential growth

Question 7

Large SD bars shows

Answer 7

A large range in variation around the means so less reliable mean value

Question 8

Small SD bars show

Answer 8

A small range of variation around the means so more accurate mean value

Question 9

Suggest why scientists recorded both percentage change and tumour volume

Answer 9

Percentage change = slows us to compare tumour as may differ in size/ volume
Tumour volume = as tumours may differ in shape

Question 10

AO3 PLAN

Answer 10

1. 2-3 comments on general trend
2. Does STUDENTS CONCLUSION match data
3. Validity = Where was the experiment data from ( computers,cultured,in test tube, not in sane environment so act with different behaviour, Petri dish ( in vitro ), ISOLATED
4. If medicine, do we know dosage, side effects
5. No stats test to see significant differences
6. Other abiotic / biotic factors that effect data
7. Reliability = sample size, length of study, season , habitat
8. Is there a Control to compare to

Question 11

When do u use t test

Answer 11

To compare 2 means to see if they are significantly different

Question 12

When do u use correlation coefficient

Answer 12

To see if link between 2 covariables is significant

Question 13

When do you use chi squared test

Answer 13

To see if differences in observed and expected values in categorical data are significantly different

Question 14

P< 0.05

Answer 14

1. There is a significant difference between mean rate of reaction
2. There is a significant increase / decrease in rate of reaction from
3. There is a less than 5% probability that significant differences are due to chance
4. Reject null hypothesis

Question 15

P>0.05

Answer 15

1. There is no significant difference in mean rate of reaction.
2. There is more than 5% probability significant difference are due to chance
3. Accept null hypothesis

Question 16

P<0.01

Answer 16

1. There is a highly significant difference between mean rate of reaction
2. There is a significant increase/ decrease in mean rate of reaction at …compared to…
3. There is less than 1% probability that significant differences are due to chance
4. Reject null hypothesis

Question 17

R= 1, P<0.05

Answer 17

1. There is a strong positive correlation between….
2. As … increases , the other factor increases
3. This relationship is significant as P<0.05, meaning less than 5 % probability that the relationship is due to chance
4. Reject null hypothesis

Question 18

R=-1, P>0.05

Answer 18

1. There is a strong negative correlation between x And y
2. as x increase , y decreases
3. The relationship is not statistically significant as P > 0.05 which means greater than 5 % probability that the relationship is due to chance
4. Accept null hypothesis

Question 19

SD bars overlap

Answer 19

There is a significant difference
( direction ) significant decrease in mean rate of reaction from 20 to 40

Question 20

SD bars don’t overlap

Answer 20

There is a significant difference
( direction ) significant increase in mean rate of reaction from 20 to 40

Question 21

What is an control used for

Answer 21

To allow comparison to the the effect of

Question 22

Describe how to set up a control

Answer 22

Set up a control with no ( to the effect of ) independent variable with all environmental factors the same ( temperature, light, PH)

Question 23

Degrees of freedom

Answer 23

N-1 ( number of different types of … -1)

Question 24

How to determine significant difference from chi squared table

Answer 24

Go down column with P=0.05
Go across column with degree of freedom value
If x2 value of greater than expected value than no significant difference, not due to chance