HSW & Maths Skills

Question 1

ALL (4) VALID CONCLUSIONS:

Answer 1

Large sample size -> SO representative

Long study -> SO can allow us to see long-term effect of (X) variable…

Control is used -> SO comparison can be made

Mean & standard deviation -> SO significant differences shown

Question 2

ALL LIMITATIONS:

Answer 2

Small sample size -> not representative

Only samples males -> females may respond differently to treatment

Only tested on ____ in a lab // in the wild -> May obtain a different data pattern

Only tested on ____ species -> might not be true to all species

NO STATS TEST -> SO differences could be due to chance

Data is SUBJECTIVE -> some people may lie

Question 3

NULL HYPOTHESIS 4 Statements

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 observed and expected ratio
[of 3:1 brown-blue eyes]

Question 4

Formula for Percentage Change

Answer 4

Final - Initial
—————– X 100
Final

Question 5

Mitotic Index =

Answer 5

Number of cells undergoing mitosis
______________________________
Total number of cells

Question 6

Correlation Coefficient:
R value of 1 = significant correlation
R value of 0 = not correlated
If the P value of a positive correlation is LESS than 0.05 it means that we REJECT the null hypothesis because?

Answer 6

there is a statistically significant result that the data is NOT due to chance
(less than 5% chance)

(OR a 95% probability that the results have a significant correlation)

Question 7

Diversity Index =

Answer 7

N (N - 1)
d = ————
Ę n (n - 1)

d = species diversity index
N = Total number of organisms of all species
n = Total number of organisms of each species
Ę = The sum of

Question 8

Why do we use percentages in biology?

Answer 8

Allows comparison
Samples/starting values differ

Question 9

Formula for calculating percentages

Answer 9

Number
——— X 100
Total number

Question 10

State the null hypothesis of a T Test

Answer 10

X (Independent) has no effect on Y (dependent)

Question 11

T-TEST - A student calculated a P value of 0.04 when testing their null hypothesis. Explain what you can conclude from this result (3)

Answer 11

• Probability that the different observed is due to random chance is 4% so difference is significant!;
• so reject null hypothesis;
• RELATE TO EXPERIMENT - Example:
Pigment A “moved” significantly “further” than group B.

OR
The no. of ____ in group A was significantly higher than the number of ____ in group B.

Question 12

HSW: Why do we use PERCENTAGE changes (e.g. % increase or % decrease)?

Answer 12

Measure the effect of X (e.g. red blood cells at sea level vs altitude)
Starting values differ / allows comparison of changes over time

Question 13

HSW: How do we increase
RELIABILITY?

Answer 13

More data collected / larger sample size
Over longer period of time / more time points
More independent variable values tested
Anomalies have less effect