Fieldwork and skills, Year 11: analysing data and evaluating an enquiry

An anomaly (also called an outlier)

提示On a scatter graph it is the point sitting far from the line of best fit.

为什么On a graph it stands apart from the trend. It may come from a mistake in measuring or recording, or it may be real and have a local cause, such as a weir that slows a river at one site. AQA asks you to identify these odd results in fieldwork data and comment on them.

Look for a cause, such as a measuring error or something unusual at the site

提示Ask why it happened before asking whether to keep it.

为什么If the odd result was a slip, such as a misread ruler, it can be left out and the reason stated. If the place really was different, the result is evidence and should stay, with an explanation. Either way the analysis must mention it: quietly removing awkward results is not honest.

describe

提示It says what happened but gives no reason.

为什么To describe is to say what the data shows: the pattern, with figures quoted. To explain is to give the reason, using geography: "because pebbles are worn down by attrition as the river carries them". A full analysis does both, and the second step usually begins with "because" or "this is due to".

Less traffic goes with better environmental quality

提示Say how one value moves as the other one moves.

为什么Linking data sets means using one set of results to help make sense of another. Here the two change in opposite directions, a negative relationship, which a scatter graph would show. The link suggests traffic may be a cause of poor quality (noise, fumes), but other things also change with distance, so it does not prove it.

Their sizes are much more varied

提示The middle half of one sample is squeezed together; the other is stretched out.

为什么An average alone hides the spread. The inter-quartile range is the spread of the middle half of the values, so a large one means a wide mix of sizes: the sediment at site B is poorly sorted. Choosing a statistic that fits the question, and saying what it shows, is part of the analysis.

Accurate

提示An archer who hits the bullseye has this quality.

为什么How close a result is to the truth depends on the equipment and how carefully it is used: a tape pulled tight, a stopwatch started on time, a ruler read at eye level. In an evaluation, say which measurements may have been off, in which direction, and how that would change the results.

Reliable

提示Getting the same answer again says nothing about whether the answer is true.

为什么Results that come out much the same when the method is repeated can be trusted not to be a fluke. That is a separate question from whether they are close to the truth: a pupil who always misses people walking behind a bus shelter would be consistent and consistently too low. (In science lessons this is called being repeatable.)

It is subjective: the score depends on personal opinion

提示Ask whose view each number really measures.

为什么Some methods measure (a tape, a counter); others ask for a judgement. Judgements differ from person to person, so the data is less reliable. Improvements include agreeing a description for each score beforehand, having the same person score every site, or averaging several people's scores.

Secondary data, such as past flow records

提示Someone else has been measuring for decades.

为什么One of the four things AQA asks for in an evaluation is other data that would have helped. Fieldwork is a snapshot of one day. Published records, old maps and photographs, and official statistics can add the long view and a wider area, and can be used to check whether your own results were typical.

Tentative

提示It begins like the word for a shelter of canvas.

为什么An evaluation ends by judging how far the conclusion can be trusted. That depends on the method (was it accurate and fair?) and on the data (was there enough, and was it typical?). With few sites and odd results, the honest wording is "the data suggests" and not "this proves", followed by what would make it firmer.