“How do you know whether your findings are valid?”
Validity is the “extent to which a concept, conclusion or measurement is well-founded and corresponds accurately to the real world” (definition as from Wikipedia). There are two main types of validity I will talk about, internal validity and external. To make sure that the results you have collected are valid, both the internal and external validity be maintained. For my case study I am going to use Jean Piaget experiments.
To make sure your results are internally valid, you must make sure the experiment is a fair test. To do this you must make sure that you have kept the independent variables the same in each experiment. This is important because changing the independent variables might change the dependent which would ruin the experiment, thus making the results not valid. In the case of Jean Piaget, in one of his experiments he controlled the independent variable when testing 15 boys. He made sure it was a fair test by making sure that there ages were ranging from 10–14 also he made sure that the bouquet of flowers.
The way to make sure your results are externally valid is by creating a missive variation in samples. The reason it makes sure the results are more likely to be valid is that making multiple results it allows you to work can see a wider spectrum of results. This can be seen in experiments made by Jean Piaget who initially only used his 3 children as test subjects however this was a very limited sampling pool. So to get his theories validated, he needed to test his claims with larger group of children.
However almost every experiment is not done perfectly every time you carry out the experiment, thus your findings will never be perfectly valid. Both internal and external validity are prone to be having externals factors which cause the validity of the results to change. An example of a factor which affects internal validity is Maturation of subject. This means that participants have changed since the first test was done on them e.g. have grown more tired, older and slower reaction time. In the case of Jean Piaget the age of the participants was the problem due to he had only a certain number of years which he could use his children as test subjects because his children will grow older and the mind would develop further. An example of a factor which affects external variables is Multiple-treatment interference. This is where effects of earlier treatments which are remembered, so the same test cannot be used on them again. In the case of Jean Piaget he couldn’t use the children he was using in the comparison of the colour with the bouquet of flowers again because they might have remembered the experiment and so this meant that they had more time to think about the relationship between the flowers and the colour, thus making it an unfair test. However through careful procedure this can be extremely limited.
In conclusion I believe that it is possible and there are many ways of knowing your results valid. And even though there is whole spectrum of problems facing scientists and psychologists in experiments, due to the precautions them take they can make sure the results are almost perfectly valid.