Compare questions: similarities and differences

Imagine a family choosing a seaside holiday from two climate graphs, for two resorts we will call P and Q. What could two graphs that each look fine be hiding? Resort P is warmest in July, at twenty-four degrees Celsius. Resort Q is warmest in January, at twenty-seven degrees. Read one at a time, each looks like a good place for a warm week, and the family books Resort Q for July. Something in those two graphs only shows up when you read them side by side. That side-by-side reading is what a compare question asks for.

Compare means set out the similarities and differences between two things, and the rule that carries it is this: both things in every sentence, joined by a comparative word. Comparative words include whereas, while, both, more than, higher and twice as, and the two that work hardest are whereas, for a difference, and both, for a similarity. Here are three sentences about two towns. A: Hootley has a station. B: Hootley has a station, whereas Perchley has none. C: Hootley has a station because it is on the main line. Which one is a compare sentence: A, B or C? B compares. It names both places and joins them with a comparative word. A describes one place only, and C gives a reason, which compare never asks for.

When a compare question gives figures, quote figures from both things, or the difference between them, and compare the trends rather than single years. In the fictional land of Owlobia, the share of people living in towns and cities in the north rose from twenty per cent in nineteen sixty to fifty-five per cent in twenty twenty. In the south it rose from sixty-two per cent to eighty-one per cent. A gap between two percentages is measured in percentage points. Twenty per cent rising to thirty per cent is a rise of ten percentage points. How many percentage points did each region rise by? The north rose from twenty to fifty-five, so fifty-five take away twenty is thirty-five percentage points. The south rose from sixty-two to eighty-one, so eighty-one take away sixty-two is nineteen percentage points. Now the answer to compare the changes, built point by point. The similarity first: both regions became more urban between nineteen sixty and twenty twenty. Then the difference in rate, with data from both: the north urbanised much faster, rising by thirty-five percentage points, whereas the south rose by nineteen. Then the difference in size: the south was still the more urban of the two in twenty twenty, at eighty-one per cent compared with fifty-five. One examiner's report on a question like this one says: "The command word 'compare' has a different requirement to 'describe', for example data from both continents is needed for the 'data mark'." The same report says the top answers came "by recognising that urban populations had increased in both Asia and North America, then providing relevant supporting data and then pointing out that the most rapid rate of urbanisation had occurred in Asia." That is a similarity, data from both, and the faster rate, in that order. Stopping after one of those three is the slip. Another examiner's report found that "candidates often only made a single comparative comment, which limited their ability to access the full three marks available." The fix is to count your comparative points against the marks before you stop. Now a weaker answer. A student writes: the north went from twenty to fifty-five per cent. The south went from sixty-two to eighty-one per cent. Every figure is right, so why is that not a comparison? No sentence holds both regions, and there is no comparative word, so they are two descriptions side by side. The fix is one sentence that holds both, joined by whereas or both. Comparing two dots is the other slip. One examiner's report says: "Some candidates focused on comparing specific years rather than the trends." The fix is to compare the change from start to end, its direction, its rate and its size. A reason is a slip too. A student adds: the north grew faster because it industrialised. One examiner's report records: "Another frequent error was the inclusion of explanations for the trends, despite the question not asking for reasons." Cross out the because, and keep the comparison.

Comparing two graphs follows the same rule, and it starts by reading both graphs before writing a word. Back to the two resorts. Resort P: warmest month July, twenty-four degrees; coldest month January, three degrees; six hundred millimetres of rain a year, wettest in November. Resort Q: warmest month January, twenty-seven degrees; coldest month July, eighteen degrees; one thousand four hundred millimetres of rain a year, wettest in February. Before any comparing, one quick sum on each graph will help. What is each resort's temperature range, warmest month minus coldest? Resort P: twenty-four take away three is twenty-one degrees. Resort Q: twenty-seven take away eighteen is nine degrees. Now four comparisons, each naming both resorts. Resort Q is warmer all year: even its coldest month, at eighteen degrees, is fifteen degrees warmer than Resort P's coldest, at three. Resort P has the much larger range, twenty-one degrees against Resort Q's nine. Resort Q is far wetter, with one thousand four hundred millimetres a year compared with P's six hundred, more than twice as much. Now the fourth comparison, the one the family missed. What does it say about the seasons? Their seasons are reversed: Resort P's warmest month is July, whereas Resort Q's is January. Resort Q is south of the equator, so a July week there is its coldest month. One examiner's report on a pair of climate graphs records the slips this avoids: answers that "wrote about Graph A and then Graph B with no comparison", and answers that "assumed that the months of June and July were the summer." The habit is to read both axes and both warmest months before you compare.

Comparing two locations means comparing where each one sits, coast against inland, north against south, upland against lowland, in compass terms. A map of Owlobia shows two cities. Penbury is on the east coast, where the River Tawny meets the sea. Talonford is about three hundred kilometres inland, in the uplands of the north-west. The first comparison is done for you: Penbury is on the coast, whereas Talonford is inland, about three hundred kilometres from the sea. Now you write the second comparison: where do Penbury and Talonford each sit? Penbury lies in the east at a river mouth, while Talonford lies in the north-west, in the uplands. Each sentence names both cities and a difference in where they sit. One tempting answer measures between them instead: Talonford is three hundred kilometres north-west of Penbury. That says how to get from one to the other, not where each one is. Of a real location question, an examiner's report notes: "Some candidates calculated distances and described the compass direction between cities in Brazil; these were not credited." One more check: compare the quantity the question names. If it asks about river discharge, compare discharge, not rainfall, so underline the quantity before you start.

Back over it, one question at a time, answers from you first.

What must every compare sentence contain? Both things, joined by a comparative word such as whereas or both, and figures from both when the question gives figures.

Now one with new figures. Region A's urban share rose from ten per cent to forty per cent, and Region B's rose from fifty per cent to sixty per cent. Which region rose faster, and by how many more percentage points? Region A rose thirty points and Region B rose ten, so A rose faster, by twenty more percentage points, three times as many.

Now the paragraph test: all of one place, then all of the other. What is missing? A sentence that holds both places with a comparative word. Two descriptions side by side are not a comparison.

Now the last check: does a compare answer give reasons? No. Compare sets out similarities and differences only, and the reasons belong to an explain question.

What were the family's two graphs hiding? Side by side, they show Resort Q's seasons reversed: July is its coldest month, at eighteen degrees, and it gets more than twice Resort P's rain. Read one at a time, that difference stayed hidden.

If there is no need to see this twice, give it a thumbs-up. If it is still settling, save it, and one past paper's pair of graphs will settle it.

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