For A Level Edexcel biology , Paper 6

1. WELCOME
6BIO8 – paper code
6B Paper discussion
By.J.Sharmila Christy
Biology Teacher , Villa International High School, Male’
Republic of Maldives

2. 6 B PAPER HAS 3 QUESTIONS
 Q1, Based on AS &A2 practical
experiments
 Be thorough in doing these practical's
, procedure, precautionary methods
 Q2. Statistical test
 5 tests for calculating mean , median, mode &
differences
 Q3.Planning an Investigation
 steps of doing, analysis & interpretation of
data

3. STATISTICAL TESTS USED
1.Correlation
Spearman Rank Test 3.Chi2 – Test
Correlate between Goodness to fit
factors
2.T – Test
MEAN 4.Wilcoxon paired Match
Test( W Test)
For paired data
5.Mann Whitney
( U– Test )
MEDIAN

4. CORRELATION COEFFICIENT
SIGNIFICANCE OF RELATIONSHIP BETWEEN 2 VARIABLES
(DV & IDV )
EG: TEMPERATURE AND RATE OF ENZYME ACTION .
SCATTERED GRAPH
Null Hypothesis – There is no significant
relationship between the independent and
dependent variable
If calculated value, at p = 0.05 , 5% significance
level, is greater than critical value , REJECT Ho
Degree of freedom = n-1 , n= no of
measurements

5. GRAPH
DV
IDV

7. T-TEST
USED IN CALCULATING MEAN VALUES
DATA IS SHOWN IN NORMAL DISTRIBUTION
GRAPH
EG: TEMPERATURE AND RATE OF ENZYME
ACTION .
SCATTERED GRAPH
Null Hypothesis : There is no significance difference
between the mean value of set one and set two
If calculated value > Critical value ,at p =0.05 (5%)
REJECT Ho
Degree of freedom = n-2

9. MANN WHITNEY ( U TEST )
 Forcomparing the MEDIAN VALUE
 Data is not normally distributed , it is skewed
Null Hypothesis : There is no significant difference
between the median values of sample 1 & sample 2
There will be two values – U1 and U2
The smaller U value is the calculated value
 If calculated value > Critical value ,at p =0.05 (5%)
ACCEPT Ho
 Degree of freedom = n-2

10. Median
Factor/ unit

11. WILCOXON MATCHED PAIRED TEST
W TEST
 Used to determine if the difference between two
sets of data measuring the same variable
 Data must be matched in pairs
 Single
unique way to link data from one set to
another
 Eg, pulse rate before & after exercise
 Usually bar graphs , with bars in pairs

12. CHI 2 TEST
 Used to measure goodness of fit
Used to test whether the difference between the
observed values are significantly different from the
expected value
 Usually bar graph in pairs
 Eg A rat is placed in such a cage
probability of rat chosing the open door
 Exp ratio : N S E W
 1 :1 :1:1
 Obser ratio 9:11:8:12
 Mostly used in genetic questions

13. NULL HYPOTHESIS : THERE IS NO SIGNIFICANT
DIFFERENCE BETWEEN THE OBSERVED &
EXPECTED VALUES
 After doing the chi2 test
 If calculated value > Critical value ,at p =0.05 (5%)
REJECT Ho
 Conclusion : There is a significant difference between
the observed and the expected value
 If calculated value < Critical value ,at p =0.05 (5%)
ACCEPT Ho
 Conclusion : There is no significant difference
between the observed and the expected value, any
difference is due to chance alone

14. RULES TO REMEMBER
 FOR W U  For T,Chi2, Corr
 Calculated  Calculated
Value >critical Value >critical
value value
ACCEPT Ho
REJECT Ho