Choosing standardised measures for an impact study

Length, language and cost are key things to consider when choosing standardised measures, says Helen Brookes

The NSPCC evaluation team has gained a great deal of experience in administering standardised measures to our service users. This helps us to find out whether the service they've attended has helped them or not, by reducing their anxiety, for example, or improving the quality of their relationship with a child.

There are a number of helpful databases that allow you to find out what scales have been developed to measure a particular construct (e.g. self esteem), such as the National Child Traumatic Stress Network’s Measures Review Database. If you’re lucky, you might find a recent systematic review that has identified and evaluated instruments to measure the construct you’re interested in.

But you can end up with a dizzying array of questionnaires. How to choose the right one for your particular project can be challenging.

This has certainly been a steep learning curve for me – and I wanted to share 5 key considerations I’ve identified.

1. Length

Think about how long your service users will have to complete the measure. Sometimes the author of the scale provides an estimate of completion time, but you could fill it out yourself and time it.

A complex questionnaire may give you more nuanced data but, if it’s too long, people may feel less inclined to complete it. This is especially the case if they will be completing many other measures, too.

2. Language

Consider how the questions are phrased. Will your service users understand what they are being asked? For example, we asked parents who had completed our Baby Steps programme to complete the Rosenberg Self Esteem Scale, but when we reviewed how it was going a few weeks in, our practitioners told us that that the language used was too complex and service users didn’t really understand the questions.

3. Cost

Many scales are freely available for anyone to use. 

For some, however, there may be a cost attached and this can vary depending on the number of copies that are used and how you administer them (electronically or on paper, for example). 

Some measures databases have copyright info listed next to the measure. If not, it's worth contacting the person who developed the measure directly and asking them. 

4. Accessible versions

Think carefully about whether you will need copies of the measure in other languages or in accessible formats.

For some widely used scales (e.g. the Hospital Anxiety and Depression Scale) validated versions are available in a range of languages and even in a format for people with learning difficulties.

When this is not the case, it’s a difficult thing to work around.

Getting a measure translated into another language is a hugely laborious and costly exercise involving translation, back translation and question testing with a sample of people who speak the language.

But, in my experience, when validated translated versions of a measure weren’t available in the language the service users spoke, it prevented those individuals participating in that part of the evaluation.

5. Reliability and validity

When choosing a measure, it’s important to choose one that is reliable and produces stable and consistent results.

Ideally, the measure you choose will have been validated with the population you’ll be using it with, so you can be sure you’re measuring what you think you are. 

If you can’t find the information you need in the literature, it can be helpful to contact the author directly. They’re usually pleased to hear about the study and happy to advise you on it.

It’s also helpful to consider how widely the measure has been used: it’s useful to compare your findings to those from other studies.

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