Cambridge International AS & A Level Biology 9700 syllabus for 2022, 2023 and 2024. Additional information
Mathematical formulae (A Level only)
Candidates are not expected to remember the formulae and symbols for the mathematical formulae in the table
below. When needed, candidates will be provided with this information.
Hardy–Weinberg equations
Key to symbols:
p = frequency of the dominant allele, e.g. A
q = frequency of the recessive allele, e.g. a
p2 = frequency of homozygous dominant genotype, e.g. AA
2pq = frequency of heterozygous genotype, e.g. Aa
q2 = frequency of homozygous recessive genotype, e.g. aa
equation 1:
p+q=1
equation 2:
p2 + 2pq + q2 = 1
Lincoln index
n1 # n2
N= m
2
Key to symbols:
N = estimate of population size
n1 = number of individuals captured in first sample
n2 = number of individuals (both marked and unmarked)
captured in second sample
m2 = number of marked individuals recaptured in second sample
Simpson's index of diversity (D)
D = 1 - d/ c n m n
N
2
Key to symbols:
n = number of individuals of each type present in the sample
(types may be species and/or higher taxa such as genera,
families, etc.)
N = the total number of all individuals of all types present in the
sample
chi-squared (χ2) test
χ2 = /
^O - Eh2
Key to symbols:
O = observed value
E = expected value
E
sample standard deviation (s)
s=
/ ^x - xrh
n-1
2
standard error (SE)
s
SE =
n
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Key to symbols:
x = observation
xr = mean
n = sample size (number of observations)
Key to symbols:
s = sample standard deviation
n = sample size (number of observations)
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Cambridge International AS & A Level Biology 9700 syllabus for 2022, 2023 and 2024. Additional information
95% confidence intervals (95% CI)
You can assume this approximation:
95% CI = xr ± (2 × SE)
Key to symbols:
xr = mean
SE = standard error
t-test
xr1 - xr2
t=
s2 s2
f 1 + 2p
n1 n2
Key to symbols:
xr = mean
s = sample standard deviation
n = sample size (number of observations)
Pearson's linear correlation (r)
r=
rr
/xy - nxy
^n - 1h s x s y
Key to symbols:
x, y = observations
xr , yr = means
n = sample size (number of observations)
s = sample standard deviation
Spearman's rank correlation (rs)
rs = 1 - f
6 # / D2
p
n3 - n
Key to symbols:
D = difference in rank between each pair of measurements
n = number of pairs of items in the sample
Number of degrees of freedom for the chi-squared test and the t-test
In both the t-test and the chi-squared test, candidates are expected to know how to calculate the number of
degrees of freedom, without being provided with the formulae.
number of degrees of freedom (v) for the chi-squared test
v=c–1
Key to symbols:
c = number of classes
number of degrees of freedom (v) for the t-test
v = n1 + n2 – 2
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Key to symbols:
n = sample size (number of observations)
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