AO3

• good external validity

  P: Schaffer and Emersons study was carried out in the families’ homes and most if the observation was actually carried out by the parents during normal activities then reported to researchers later

  E: This means that the behaviour of babies was unlikely to be affected by the presence of a researcher

  E: There is an excellent chance participants behaved naturally while being observed

  L: We can therefore say the study has good external validity
• longitudinal design

  P: A strength of the study is that it was carried out longitudinally

  E: This means that the same children were followed up and observed regularly

  E: The quicker alternative would have been to observe different children at each age- called a cross sectional design

  L: However longitudinal designs have more internal validity than cross sectional designs because they do not have the confounding variable of individual differences between participants (participant variables)
• limited sample characteristics

  P: The sample size of 60 babies and their careers was good considering the large volume of data gathered on each participant

  E: However, the fact that all families involved were from the same district and social class in the same city and at a time over 50 years ago is a limitation

  E: Child rearing practices differ from one culture to another and one historical period to another

  L: These results dont necessarily generalise well to other social and historical contexts