Statistics common mistakes

Common mistakes

• Statistical sampling common mistake 1

  Writing a final answer without showing the method that justifies it. This can weaken answers for: K1 Understand and use the terms population and sample; use samples to make informal inferences about the population; understand and use sampling techniques including simple random sampling and opportunity sampling; select or critique sampling techniques in context, including understanding that different samples can lead to different conclusions about the population..

  Fix itShow the method first, then give the final answer in the required form. Apply this directly to Statistical sampling.

• Single-variable data diagrams common mistake 1

  Writing a final answer without showing the method that justifies it. This can weaken answers for: L1 Interpret diagrams for single-variable data, including understanding that area in a histogram represents frequency; connect to probability distributions..

  Fix itShow the method first, then give the final answer in the required form. Apply this directly to Single-variable data diagrams.

• Scatter diagrams and regression lines common mistake 1

  Writing a final answer without showing the method that justifies it. This can weaken answers for: L2 Interpret scatter diagrams and regression lines for bivariate data, including recognition of scatter diagrams with distinct sections of the population; understand informal interpretation of correlation; understand that correlation does not imply causation; calculations involving regression lines are excluded..

  Fix itShow the method first, then give the final answer in the required form. Apply this directly to Scatter diagrams and regression lines.

• Central tendency and variation common mistake 1

  Writing a final answer without showing the method that justifies it. This can weaken answers for: L3 Interpret measures of central tendency and variation, extending to standard deviation; calculate standard deviation, including from summary statistics..

  Fix itShow the method first, then give the final answer in the required form. Apply this directly to Central tendency and variation.

• Outliers and data presentation common mistake 1

  Writing a final answer without showing the method that justifies it. This can weaken answers for: L4 Recognise and interpret possible outliers in data sets and statistical diagrams; select or critique data presentation techniques in context; clean data including dealing with missing data, errors and outliers..

  Fix itShow the method first, then give the final answer in the required form. Apply this directly to Outliers and data presentation.

• Mutually exclusive and independent events common mistake 1

  Writing a final answer without showing the method that justifies it. This can weaken answers for: M1 Understand and use mutually exclusive and independent events when calculating probabilities; link to discrete and continuous distributions..

  Fix itShow the method first, then give the final answer in the required form. Apply this directly to Mutually exclusive and independent events.

• Conditional probability common mistake 1

  Writing a final answer without showing the method that justifies it. This can weaken answers for: M2 Understand and use conditional probability, including tree diagrams, Venn diagrams and two-way tables; understand and use the conditional probability formula P(A|B) = P(A and B) / P(B)..

  Fix itShow the method first, then give the final answer in the required form. Apply this directly to Conditional probability.

• Probability modelling common mistake 1

  Writing a final answer without showing the method that justifies it. This can weaken answers for: M3 Model with probability, including critiquing assumptions made and the likely effect of more realistic assumptions..

  Fix itShow the method first, then give the final answer in the required form. Apply this directly to Probability modelling.

• Discrete and binomial distributions common mistake 1

  Writing a final answer without showing the method that justifies it. This can weaken answers for: N1 Understand and use simple discrete probability distributions, excluding calculation of mean and variance of discrete random variables; use the binomial distribution as a model and calculate probabilities using the binomial distribution..

  Fix itShow the method first, then give the final answer in the required form. Apply this directly to Discrete and binomial distributions.

• Normal distribution common mistake 1

  Writing a final answer without showing the method that justifies it. This can weaken answers for: N2 Understand and use the Normal distribution as a model; find probabilities using the Normal distribution; link to histograms, mean, standard deviation, points of inflection and the binomial distribution..

  Fix itShow the method first, then give the final answer in the required form. Apply this directly to Normal distribution.