A company selling plant food posts "Our plant food doubles growth!" with no numbers. A university greenhouse posts a data table of heights for 30 treated and 30 untreated plants. Which source is the more credible source, and why?

A class wants a claim it can test with an investigation. Which claim could the class actually settle by collecting quantitative data?

A claim becomes easier to trust when the source shows the data it was based on.

A student blog says a stream "felt much warmer than last week." A university weather station posts thermometer readings of 14 C last week and 15 C this week. What makes the station report the stronger evidence?

One site tested 3 batteries once and reports the mean run time. Another tested 60 batteries in repeated trials and reports the mean. Why is the second site's mean better supported?

A drink company publishes its own study saying its drink beats water for hydration. Why should a reader be careful with that report?

A website reports that as ice-cream sales rose each summer month, pond water temperature also rose, and concludes ice-cream sales warm the pond. What is the best conclusion from that data?

A claim with no evidence becomes credible once it has been copied onto many different websites.

Two sources disagree about how fast a hillside is eroding. What extra information would best help a class decide which source to trust?

A shoe company's page claims its new running shoe makes runners faster and prints five happy customer quotes. What evidence would best settle the claim?

A factory that pipes water into a lake publishes a page saying the lake is healthy. A volunteer monitoring group publishes monthly oxygen and temperature measurements. Which source better supports a claim about the lake, and why?

Two reports each state that a soil sample held 45 mL of water. Only one report also describes the graduated cylinder used and the steps followed. Why does that make the second report stronger?

A class checks which note in a field report is quantitative data. Which note records quantitative data?

A source posts a bar graph of rubbish collected at four beaches, but no unit is given for the bars. What should a reader ask before using the graph as evidence?

A class needs current air quality data for its town. One source posts measurements taken 40 years ago, and another posts measurements from last month. Which source better supports a claim about the air today?

A blog post says, "My cousin took a vitamin drink and his cold went away in two days, so the drink cures colds." Why is that weak evidence?

An advertisement claims a kitchen cleaner is "amazing on grease." How could a class turn that claim into an investigable question?

A snack maker reports that a new snack "boosts memory," based on a survey of 8 friends of the owner. What is the clearest weakness in that evidence?

A science report that other scientists checked before it was published is usually more reliable than a report that no one checked.

A school newspaper wants a rule for judging science claims found online. Which rule best matches how scientists evaluate a source?