A study reports only the average but not the spread of data. What information may be hidden?

Correct answer: How much the values varied

Direct answer: Option A, how much the values varied. An average gives one central value, but it does not show whether the individual measurements were close together or widely separated. For example, two groups can both have an average of 10: one may contain 9, 10, and 11, while another may contain 1, 10, and 19. Their averages are equal, but their spread is very different. Step by step: collect all values; calculate the average; examine how far values lie from that average; report a measure or description of spread. Option A is correct because missing spread hides variation, consistency, and possible unusual values. Option B is wrong because the independent variable can usually be named separately in the method or table. Option C is wrong because the experiment date is not what spread describes. Option D is wrong because scientist experience is unrelated to numerical variation. Memory cue: average tells the centre; spread tells how scattered the data are.