11 mistakes learners make with working scientifically, each one named and explained.
A result only answers the question when one thing was changed and everything else was held still.
Temperature against time is drawn as separate bars, so the values in between look as though they do not exist.
Bar charts are the first chart anyone learns and they work for almost everything in primary school.
Question. Temperature measured every 2 minutes
A common answer. Draw a bar for each time
The answer. Draw a line graph with time along the bottom
Why. Time and temperature both run smoothly, so the points in between are real.
Ask whether a value halfway between two readings could exist. If it could, use a line.
You tested two fertilisers on cress and conclude that this fertiliser is best for all plants.
A conclusion feels weak unless it sounds general, and the experiment did work.
Question. Two fertilisers, tested on cress, over one week
A common answer. Fertiliser A is best for growing plants
The answer. Fertiliser A grew taller cress than fertiliser B over one week
Why. The conclusion may only mention what was actually tested.
Write the conclusion using the words from your own method.
Ice cream sales and sunburn rise together, so you conclude that ice cream causes sunburn.
Two things moving together is exactly what a cause looks like on a graph, and the graph is real.
Question. Ice cream sales and sunburn, both rising in June
A common answer. Ice cream causes sunburn
The answer. Both rise with hot, sunny weather
Why. A link is a reason to look for the cause, not the cause itself.
When two things rise together, ask what third thing might be moving them both.
You say the result is accurate because you repeated it five times, although the balance was never zeroed and every reading is 2 g too high.
Repeating is drilled as the thing that makes results trustworthy, so it gets used as a general repair rather than for what it actually fixes.
Question. A balance reading 2 g with nothing on it
A common answer. Repeat the measurement five times and take the mean
The answer. Zero the balance, then repeat five times and take the mean
Why. Repeats reduce random scatter. They cannot remove an error that repeats itself.
Repeats deal with scatter. Only checking the equipment deals with a shift.
Every volume comes out a millilitre or two high, because the reading is taken where the water climbs the glass rather than at the bottom of the curve.
The water at the edge is the part at eye level and the part you notice first.
Question. Water in a measuring cylinder, curve between 24 and 25 ml
A common answer. Read 25 ml, at the top of the curve
The answer. Read 24 ml, at the bottom of the curve, with your eye level with it
Why. The curve is the water gripping the glass, so the flat middle is the real level.
Get your eye level with the liquid and read the flat part.
Readings of 24, 25, 24 and 62 are averaged to 33.75, and the mean now describes none of them.
Leaving a number out feels like changing the result to suit yourself, so every number is kept.
Question. 24, 25, 24 and 62
A common answer. Mean = 33.75
The answer. Leave 62 out as an anomaly, mean of the rest = 24.3
Why. An anomaly is a reading the method went wrong on, not a reading you dislike.
Identify anomalies before averaging, say which ones you left out, and say why.
Your graph is a zigzag from point to point, so the trend disappears and a reading taken between two points means nothing.
Joining the dots is what a dot to dot taught, and it does use every point, which feels honest.
Question. Eight points that rise with some scatter
A common answer. Join each point to the next with a ruler
The answer. Draw one straight line with the points balanced either side of it
Why. The line shows the pattern. The scatter is the measuring, not the science.
One line through the trend, with roughly as many points above it as below.
You read a thermometer marked every 2 degrees as though every mark were 1 degree, so the reading is out by half.
Most scales a learner meets are marked in ones, so the eye fills in ones without checking.
Question. A scale with 5 gaps between 20 and 30
A common answer. Each small mark is 1 degree
The answer. Each small mark is 2 degrees, because 10 degrees is split into 5
Why. Count the gaps between two labelled marks, then divide.
Before the first reading, work out what one small division is worth.
You call the temperature the independent variable in an enquiry where temperature is what the thermometer reads at the end.
Both variables are numbers that change during the experiment, so the two roles blur.
Question. Does more insulation keep water warm for longer?
A common answer. Independent variable: the temperature of the water
The answer. Independent variable: the number of layers of insulation
Why. You choose the layers. The temperature is what the layers do to the water.
Ask which one you could write into the plan before touching any equipment.
What you changed is up the side and what you measured is along the bottom, so the graph reads backwards against every other graph in the class.
Nothing in the numbers says which way round they go, so the first axis drawn takes whichever column was written first.
Question. Layers of insulation against temperature
A common answer. Temperature along the bottom, layers up the side
The answer. Layers along the bottom, temperature up the side
Why. What you chose goes along the bottom, what you measured goes up the side.
Independent along the bottom, dependent up the side, every time.
Your plan changes the mass and the height of the ramp together, so whatever the result is, it cannot say which change caused it.
Changing two things feels like covering more ground in one go, and the plan still looks and reads like a proper experiment.
Question. Testing whether a heavier trolley rolls further
A common answer. Use a heavier trolley and make the ramp steeper
The answer. Use a heavier trolley and leave the ramp exactly as it was
Why. One change gives one explanation, two changes give two.
Name the one thing you will change, then write the list of everything you are holding still.
WAJD spots these patterns in your child's answers and names the one behind their wrong answers, instead of just marking them wrong.