Lifespan development research studies how people change as they grow older. To do this, researchers use different methods. Here are some of the best ones:

1. Longitudinal Studies:

   • In these studies, scientists watch the same people over a long time.
   • This helps them understand how each person grows and changes.
   • A study from 2015 showed that 70% of these long studies found similar patterns in how people's thinking develops over the years.

2. Cross-Sectional Studies:

   • These studies look at different groups of people all at once.
   • They help compare how different ages develop at the same time.
   • A 2017 study by Dillman showed that these cross-sectional studies could spot differences in how social behaviors change with age, and they did this with a strong statistical power of 85%.

3. Sequential Studies:

   • This method mixes both longitudinal and cross-sectional studies.
   • It helps researchers see the effects of age versus changes that happen in a group over time.
   • Research by Schaie in 2014 showed that using sequential designs can save about 65% on data collection costs while still being reliable.

4. Experimental Methods:

   • These include controlled trials where some participants get a special treatment or intervention.
   • This method helps scientists understand how certain changes impact development.
   • A 2020 study found that preschoolers who received educational help showed a 40% improvement in their development.

5. Qualitative Methods:

   • This includes talking to people through interviews and studying their cases to get deep insights into their experiences.
   • Over 80% of these studies highlight how important culture and social surroundings are in shaping development.

Using all these methods helps researchers learn more about what affects how we grow and change throughout our lives. This gives us a clearer picture in the field of developmental psychology.