page 10 17. A student was planning an investigation into the effect of temperature on the rate of respiration in yeast; this was measured using a carbon dioxide probe. As part of their pilot studies, they used the probe to take three readings from one sample. This would be most useful for checking A precision B accuracy C reliability D validity. 18. The diagram shows a boxplot for a set of data. R S T U V Which statement about the dataset represented by this boxplot is true? A T is the mean value B R minus V is the interquartile range C 50% of the data are above U D 75% of the data are below S 19. Which row in the table describes natural killer cells? Type of response Mechanism of action Specific Non‑specific Induce apoptosis in parasite‑infected cells Use enzymes in lysosomes to digest parasites A ✓ ✗ ✓ ✗ B ✓ ✗ ✗ ✓ C ✗ ✓ ✓ ✗ D ✗ ✓ ✗ ✓