How to Read Thermometer Charts

The LibQUAL+® survey asks participants to assess the quality of library service delivery using three criteria:

  • Perceived service level – what the user sees.
  • Desired service level – what the user wants.
  • Minimum acceptable service level – the lowest acceptable level of service.

Thermometer charts allow analysis of these three criteria in relation to each other:

  • Green boxes on the charts = perceived service level.
  • Top of the blue bar = desired service level.
  • Bottom of the blue bar = minimum acceptable service level.

Looking at these three data points together facilitates a clearer understanding of how our users feel about our services than looking at each of them in isolation. For example, a perceived score of 6.3 on a 9 point scale might be interpreted as average. However, if the minimum acceptable service level is a 3.1 and the desired service level is a 7, then we are doing very well. Our performance is close to what the user desires. On the other hand, if the minimum acceptable service level is a 3.1 and the desired level is 8.2, the assessment that users view our performance as average would be accurate.