9.2 - Recording Results in a Table

What a table question looks like

• The N5 paper asks you to work with tables - either design one to record readings, or complete one that's partly filled in.
• The marks are for the structure of the table, not the biology.

A typical question

A student is going to measure the time taken for starch to disappear when amylase is added, at five different temperatures. Each temperature is tested three times.

Draw a table the student could use to record the results.

The three things that earn the marks

1. Draw it as one table with enough columns and rows, and a ruled line under the headings.
2. Head each column with the quantity and its unit, written as "quantity / unit".
3. Record every reading in the right place, to a consistent precision.

Completing a table:

• When the paper gives the readings already and asks you to complete or process a table, the same three things are marked - plus any calculation, such as a mean.
• The rules never change from one experiment to the next, so this is a dependable source of marks.

Setting out a results table

• A results table gives every number you collect a place, laid out so the pattern can be read down the columns.
• Draw it before you start, so you're not designing it while readings are coming in.

How to lay it out

• Put the variable you change in the first column, with its values going down in order.
• Give the variable you measure a column for each repeat, plus a final column for the mean.
• So testing five temperatures three times each needs: one column for temperature, three repeat columns, and one mean column - five in total.
• Draw the whole thing with a ruler, including a ruled line under the headings - a heading that "floats" with no line under it can lose the structure mark.

Worked example - Table for an amylase experiment

Set out a table to record the time for starch to disappear at 20, 30, 40, 50, and 60 °C, with three repeats at each temperature and a column for the mean.

Table headings and units

• Write each column heading as the quantity followed by its unit, separated by a slash - for example "Temperature / °C", "Time / s", "Length / mm".
• Writing the quantity but leaving off the unit is one of the commonest ways to lose credit.
• The slash reads as "temperature divided by the unit", so the numbers underneath are written as plain numbers with no unit beside them.
• Put the unit in the heading once, not after every value.

Choosing the right unit

• Match the unit to the instrument: a stopwatch reads in seconds, so the heading is "/ s", not "/ min".
• Do not use "m" for minutes - it reads as metres.

Filling in the readings

• Record the actual measured value, not a label - if one tube was in hot water and one in cold, write the temperatures you measured (e.g. 45 °C and 12 °C), not the words "hot" and "cold".
• Every cell holds a number - the table is a record of measurements.

Keep the precision consistent

• Keep the same precision all the way down a column - don't write 42 in one row and 42.5 in the next.
• The precision should match what the instrument can show:
  • A stopwatch reading to the nearest second - every time ends in a whole number of seconds.
  • A thermometer marked every degree - read to the nearest degree, not to a tenth.

Calculating the mean

• Where a table has repeats, the last column is the mean.
• Add the repeats for that row and divide by how many there are.
• Round the mean to the same precision as the readings it came from.
• If a repeat is clearly anomalous - an odd one out well away from the others - leave it out of the mean and note it.

Common exam questions

Question 1

A student counted the stomata on the upper epidermis of five leaves and needs to complete the table to include the number on the lower epidermis, then find the mean. What has to go in the last column, and how is it worked out?

A mean column: add the five counts for the lower epidermis and divide by five, rounding the mean to the same precision (a whole number of stomata) as the readings it came from.

Question 2

How should the heading of a column that records temperature in degrees Celsius be written?

As "Temperature / °C" - the quantity, then a slash, then the unit - so the values below can be written as plain numbers.

Question 3

A student writes "20 °C, 30 °C, 40 °C" down the temperature column of a table. Where should the unit go?

In the heading, once, as "Temperature / °C". That is the convention markers look for, and it leaves the values below as plain numbers.

Question 4

An experiment measures the time for a colour to change at five temperatures, with three repeats at each. How many columns should the table have, and what is the last one for?

Five columns: one for the temperature, three for the three repeats, and a final column for the mean time.

Question 5

One of the three repeats for a temperature is much higher than the other two. What should you do with it when finding the mean?

Treat it as an anomaly, leave it out of the mean, and find the mean from the two consistent repeats.