Woman with dyed blonde hair

Take care with your sample

“Recommended by 93% of ‘Red’ readers”

The Advertising Standards Authority (ASA) banned a TV advert for hair product Nice ’n Easy in 2009. The advert included a voiceover that said “93% of ‘Red’ magazine readers would recommend Nice ’n Easy to a friend. The other 7% probably don’t have any friends.”

Afterwards, some text flashed up on the screen: “Participants in a survey of 245 ‘Red’ magazine readers, April 2008”. The problem wasn’t so much the small sample (though a professional opinion survey typically covers at least 1,000 people) as the way the data were collected. Participants had volunteered to take part in the survey and were sent a pack of the hair dye, as well as the survey (which included a question about whether they would recommend the product to a friend). If they returned the survey, along with a photo of themselves and a short story, they had a chance of winning a trip to New York.

The ASA banned the advert because they believed the claim of 93 per cent was misleading. It said: “We were concerned that the...respondents entering the competition were selected on the merits of their competition entry [the short story] and may have been inclined to be less than impartial in their survey responses in order to stand a better chance of winning.”

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Questions for discussion

  • How many of a magazine’s readers should you ask before you can make claims about the opinions of its readership?
  • Is it OK to provide incentives to people taking part in surveys? Will you get the same results, or will the incentive skew the findings?
  • Is there any guarantee that the people filling in the survey actually tried the hair dye they were sent? How could it have been done differently?

About this resource

This resource was first published in ‘Number Crunching’ in June 2013.

Topic:
Statistics and maths
Issue:
Number Crunching
Education levels:
16–19, Continuing professional development

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