Without younger sibling

At first glance it is apparent that the scores seem to follow the direction predicted in hypothesis 1, that is that females on average have scored higher than males on the questionnaire testing their knowledge of developmental norms. As the data collected from this questionnaire is interval data and the design in an independent groups design, the appropriate statistical test to see if the difference is statistically significant or not is the unrelated T-test (see appendix for calculations).

The critical value for a one-tailed test with a degree of freedom of 71, using a significance level of 0. 5 is 1. 6666. The number calculated from these results is 1. 55 and this number must be higher than the critical value to be significant, and therefore although there is a difference, it is not large enough to ensure it had not occurred simply by chance. Hypothesis 2 Table to Show the Mean Score of Those with Younger Siblings and Those Without on a Test on Developmental Norms Table 2 Mean Score Have younger sibling 12. 75 Have no younger sibling 12. 15 Graph 2

Once again at first glance the results do appear to be consistent with the prediction made by the experimental hypothesis, that those who have younger siblings will know more about developmental norms than those without. As the experimental design is the same as before, an unrelated T-test will be used to test the significance of this result also (see appendix) The value calculated from these results is 0. 737 which does not exceed the critical value of 1. 666 making the difference between these two results not significant enough to allow us to accept the experimental hypothesis.

Table to Show the Mean Score of Those with Siblings and Those Without on a Test on Developmental Norms Table 3 Mean Score Have sibling 12. 46 Have no sibling 12. 8 Graph 3 For this hypothesis, from both the graph and the table of means it is evident that the trend was in the opposite direction to that predicted. The group with no siblings performed better than those who did have siblings. Because of this, a statistical test will not be conducted as the hypothesis was one-tailed and therefore does not allow the results to be significant if the trend was in a different direction.


The aim of this study was to see if gender or whether having a sibling younger or otherwise had an effect on knowledge of developmental norms. None of the three experimental hypotheses were proved statistically significant despite previous research suggesting that they would be. In all three instances the group sizes were unequal which could be to blame, as a smaller group is less likely to be representative of the population it is from and makes spotting anomalies or unusual results harder to distinguish. This was especially the case for hypothesis 3 in which the ‘no siblings’ condition consisted of only 5 people.

The results collected for this hypothesis were also the ones furthest away from the anticipated outcome (the trend was in the opposite direction to that predicted) which suggests this may have been a factor. This problem was mainly down to the sampling method, as participants were selected on their availability rather than their belonging to the various conditions. To counteract this issue while not entirely sacrificing the speed and ease of opportunity sampling, quota sampling could be used as this would ensure equal group sizes.

The questions on the questionnaire were devised in 1984 which means that they could also be out of date. IQ tests and other similar forms of assessment are regularly revised and re-standardised to account for the changes in society and modern life that result in changes in ‘normal’ intelligence and development. Therefore its is likely norms have changed over the last 11 years and so it is possible that the hypotheses generated unsigificant results because the participants were answering the questions in accordance with the modern speed that children are developing at, not that of 11 years ago.

Additionally, it may be possible the results for hypothesis 2 (with the conditions of having younger siblings or not) to be more significant if the age difference between the participant and their sibling was to be taken into account. This is because if there is only a year between them, for example, it is unlikely that they will have any recollection of their development and so be in the same position as those without younger siblings.

These findings do suggest, however, that it is possible that gender and presence of younger or older siblings does not affect participants’ awareness of the age at which children are able to accomplish certain goals. If this were the case, it would mean that women do not have a more innate understanding of this than men and so it is therefore learnt from the environment. Having said this, if having a younger sibling does not affect their knowledge either, the environment in which it is learnt is not isolated to their own home and their own family members.

A suggestion for further research could subsequently be to also ask the participants questions concerning their interaction with children in order to take this factor into consideration.


Griffiths, R. (1984). The Abilities of Young Children. High Wycombe: The Test Agency Slater, A and Bremmer, G. (2003). An introduction to developmental psychology. Blackwell. Slater & Lewis (2002), Introduction to infant development. Oxford: Oxford University Press Dumont & Williams. (2001). Wechsler Intelligence Scale for Children. Retrieved November 22nd, 2005, from http://alpha. fdu. edu/psychology/WISC-III%20Descrpition_. htm

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