Unit 8 · Detecting Reasoning Errors
Two Frog Species — Detect the Flaw
Lesson 18 of 34
About this lesson
113 red sentinels were spotted. Only 15 speckled greenbacks. Melissa concludes red sentinels are much more common. But what if one species is simply harder to see? Counting sightings is not the same as counting frogs.
Chapters
Question
Two different species of frog are known to live on the Quilpie Nature Reserve: speckled greenbacks, and red sentinels.
Ahmed and Melissa are investigating the populations of the two species, and have done an experiment.
Ahmed said: “For a whole year, every time a frog was spotted on the reserve, we made a note of which species it was. Over the year, we recorded 113 red sentinels and only 15 speckled greenbacks.”
Melissa said: “That tells us that red sentinels are much more common on this reserve, and speckled greenbacks are actually quite rare.”
Which one of the following sentences shows the mistake Melissa has made?
Take your Selective prep further
- Sample questions & worked solutions across core Selective topics
- Digital exam simulator with interactive practice sets
- Personalised progress tracking across all your devices
Already have an account? Log in here
No payment required. Compare Selective plans
Give Your Child the Best Chance at Selective Entry
Join NSW families preparing their children for the Selective Schools Placement Test with the most realistic online Selective practice tests available. First tests free—no credit card required.
Claim Your Free Selective Practice Tests