Research methods
50 exam-style questions with answers for 3.7 Research methods in AQA A-level Environmental Science (spec 7447). Practise with flashcards, a topic quiz, a random quiz across the course, 5 crosswords, Five Degrees, Associations, or read every question and answer below. Not official AQA material.
All 50 questions and answers
Question 1
Justify the use of a transect. [1 mark]
Answer:There is an environmental gradient, so sampling at regular intervals along a line shows how conditions change with distance.Question 2
Describe how the Lincoln index estimates population size. [3 marks]
Answer:Capture, mark and release individuals, then recapture later. Population = (number in first sample × number in second sample) ÷ number of marked recaptures. It assumes no births, deaths or migration and even mixing.Question 3
What does p = 0.05 mean? [1 mark]
Answer:There is a 5% probability that the result occurred by chance, so the null hypothesis is rejected if p is 0.05 or less.Question 4
Justify the use of random sampling. [1 mark]
Answer:It avoids bias in choosing sample sites.Question 5
Explain why a large number of samples is needed. [2 marks]
Answer:It gives a reliable mean that reduces the effect of anomalies, and allows statistical tests.Question 6
Define the term ‘standardisation’. [1 mark]
Answer:Keeping variables and techniques the same so results can be compared validly.Question 7
Describe how a grid quadrat finds percentage cover. [2 marks]
Answer:Place the quadrat at random, count the squares covered by the species, and express as a percentage of the total.Question 8
State the formula for Simpson’s index of diversity. [1 mark]
Answer:D = N(N − 1) ÷ Σn(n − 1), where N is the total number of organisms and n is the number of each species.Question 9
Describe how kick sampling works. [2 marks]
Answer:Disturb the stream bed for a set time upstream of a net, then identify and count the invertebrates collected.Question 10
Explain how a Tullgren funnel works. [2 marks]
Answer:Heat and light drive soil invertebrates downwards into a collecting beaker.Question 11
Name a statistical test for correlation. [1 mark]
Answer:Spearman’s rank correlation coefficient.Question 12
State when a chi-squared test is used. [1 mark]
Answer:For count data in categories, comparing observed with expected values.Question 13
State when a Mann–Whitney U test is used. [1 mark]
Answer:To compare two sets of data that may not be normally distributed.Question 14
State what standard deviation shows. [1 mark]
Answer:The spread of data around the mean. Overlapping ranges suggest no significant difference.Question 15
Describe how soil moisture is measured. [2 marks]
Answer:Weigh a sample, dry it to constant mass, and calculate the mass lost as a percentage.Question 16
Define the term ‘transect’. [1 mark]
Answer:A line along which samples are taken to study change across an environmental gradient.Question 17
Distinguish between systematic and random sampling. [2 marks]
Answer:Systematic sampling uses regular intervals and suits a gradient. Random sampling avoids bias where there is no gradient.Question 18
Describe how a pitfall trap works. [2 marks]
Answer:A cup sunk into the soil with a cover catches ground invertebrates that fall in.Question 19
State the Lincoln index formula. [1 mark]
Answer:Population = (n1 × n2) ÷ m, where m is the number of marked individuals recaptured.Question 20
State two assumptions of the Lincoln index. [2 marks]
Answer:No births, deaths or migration, marks are not lost, and marked individuals mix evenly.Question 21
Describe how light intensity is measured. [2 marks]
Answer:Hold a light meter at vegetation height and record the maximum over a set time.Question 22
Explain why sample timing matters. [2 marks]
Answer:Weather, season or time of day affect results, so timing must detect variability.Question 23
Explain how to decide the number of samples. [2 marks]
Answer:Take increasing numbers of samples until the mean stops changing significantly.Question 24
Describe how a sweep net is used. [2 marks]
Answer:Sweep in a figure of eight through vegetation for a set time, then count the insects caught.Question 25
Describe how a Secchi disc measures turbidity. [2 marks]
Answer:Lower the disc until it disappears and record the depth.Question 26
Describe how bat detectors work. [2 marks]
Answer:They detect ultrasound calls, and the frequency identifies the species.Question 27
State what is meant by percentage error. [1 mark]
Answer:The uncertainty in a measurement as a percentage of the measurement.Question 28
Describe how soil pH is tested. [2 marks]
Answer:Mix soil with distilled water, add universal indicator and compare with the colour chart, or use a calibrated meter.Question 29
State what a null hypothesis says. [1 mark]
Answer:There is no significant difference or correlation between the variables.Question 30
Explain how to decide if a result is significant. [2 marks]
Answer:Compare the test value with the critical value at p = 0.05 for the degrees of freedom.Question 31
Distinguish between accuracy and precision. [2 marks]
Answer:Accuracy is how close a measurement is to the true value (1); precision is how close repeated measurements are to each other (1).Question 32
Define the term ‘reliability’ of data. [1 mark]
Answer:The extent to which repeating the investigation gives consistent results.Question 33
Define the term ‘validity’ of an investigation. [1 mark]
Answer:Whether the investigation measures what it claims to measure, with other variables controlled.Question 34
Distinguish between independent, dependent and control variables. [3 marks]
Answer:Independent: the variable deliberately changed (1); dependent: the variable measured (1); control: variables kept constant so a fair test is carried out (1).Question 35
Describe how to estimate population density using quadrats. [3 marks]
Answer:Place quadrats at random positions using random numbers (1); count the individuals in each quadrat (1); calculate the mean per quadrat and scale up to total area: mean x (total area / quadrat area) (1).Question 36
Distinguish between a line transect and a belt transect. [2 marks]
Answer:Line transect: species touching a line are recorded at set intervals (1); belt transect: a strip of set width, using quadrats along the line to record abundance (1).Question 37
Explain what a confounding variable is. [2 marks]
Answer:An uncontrolled variable other than the independent variable (1); it affects the dependent variable, so the results may be misleading (1).Question 38
Describe how to measure wind speed in the field. [2 marks]
Answer:Use an anemometer held at a standard height (1); take several readings and calculate the mean, facing the wind (1).Question 39
Describe how dissolved oxygen in water is measured. [2 marks]
Answer:Use a dissolved oxygen probe/meter placed in the water sample (1); calibrate it and take repeated readings at the same depth and temperature (1). Alternative: Winkler titration.Question 40
Explain how Biological Oxygen Demand (BOD) indicates organic pollution. [3 marks]
Answer:Measure dissolved oxygen in a sample, incubate in the dark at 20°C for 5 days and measure again (1); the oxygen used up is the BOD (1); high BOD means high organic pollution, because microbes use more oxygen (1).Question 41
Explain how a biotic index is used to assess water quality. [3 marks]
Answer:Indicator species have known tolerances to pollution (1); presence/absence or abundance of these species gives a score (1); high scores/pollution-sensitive species show clean water; low scores show pollution (1).Question 42
State what overlapping standard deviation bars suggest. [1 mark]
Answer:That the difference between the two means may not be significant.Question 43
State the meaning of correlation coefficients of +1 and –1. [2 marks]
Answer:+1 is a perfect positive correlation (1); –1 is a perfect negative correlation (1).Question 44
Explain why correlation does not prove causation. [2 marks]
Answer:Two variables may change together because of a third factor (1); the relationship may be chance, so experimental evidence is needed to show cause (1).Question 45
State when a t-test is used. [1 mark]
Answer:To compare the means of two samples of normally distributed data.Question 46
Describe how to calculate percentage change. [2 marks]
Answer:Subtract the original value from the new value (1); divide by the original and multiply by 100 (1).Question 47
Describe ethical considerations in fieldwork. [2 marks]
Answer:Minimise disturbance and damage to habitats and organisms (1); return organisms and replace rocks and stones where found, avoid trampling and take only the minimum samples needed (1).Question 48
Describe how a risk assessment is used in fieldwork. [2 marks]
Answer:Identify hazards such as weather, deep water, ticks and unstable ground (1); decide who may be harmed and put control measures in place, eg life jackets, a group leader and protective clothing (1).Question 49
Describe how remote sensing is used to monitor ecosystems. [2 marks]
Answer:Satellites or drones record images/reflectance data over large or inaccessible areas (1); eg vegetation cover, forest loss or sea ice change can be monitored over time using GIS (1).Question 50
State why random sampling is used to reduce bias. [1 mark]
Answer:Every location has an equal chance of being chosen, so the researcher’s preferences do not influence the results.