• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

Statistical Analysis for IB Psychology. The chi-square test is a method of statistical analysis used for comparison of observed/ actual data to expected data.

Extracts from this document...

Introduction

Chi-Square Test The chi-square test is a method of statistical analysis used for comparison of observed/ actual data to expected data. Chi-squared asks and answers the question, "Does my observed data fit with my expectations?". It is measured as the probability for your event to occur, p> .05 or p<.05. The higher your x2 (chi-square) value, the less likely your results are accurate (or due to chance). The lower the value, the more accurate, or likely to occur. Example: A restaurant owner expects that over the course of 6 days, 10% will come in on Monday, 10% on Tuesday, 15% on Wednesday, 20%on Thursday, 30% on Friday, and 15% on Saturday. This is his 'Expected distribution'. The null hypothesis would be that: H0= The owner's distribution is correct and the alternative hypothesis would be: H1= The owner's distribution is incorrect We want to accept or refute the null using the significance of ? =.05, or 5%, to see what the probability of getting a result of this, or more extreme (p<.05), would be. ...read more.

Middle

Critical Chi-Square Value: Determine the Degrees of Freedom - We're taking 6 sums (6 days), so you may be tempted to say Degrees of Freedom =6, but if you have the first 5 values, you could find out the 6th, so we only have 5 Degrees of Freedom. We can say Degrees of Freedom = n-1 So, Our degree of freedom (D.F) is 5, our P value/significance is .05 or 5%, We can determine that our Critical chi-square value (?2c) is 11.07. Our D.F. is 5, so k=5 (magenta) If we continued the line, we would see that as the D.F. increases, the probability decreases. T-Tests The t- test is a method of statistical analysis used for comparison of sets of data. A t-test asks and answers the question, "Which set of data is higher?". The comparison must take into consideration the variability of data. Example: Hypothesis: Fluoride water prevents tooth decay. To test, the researcher looks at 5 communities that do have fluoride water, and 5 that do not. The dependent variable is the percent of the population with tooth decay, so a higher number is bad. ...read more.

Conclusion

sample one PLUS the Sample Variance of sample 2 SQUARED OVER number of observations in sample 2 So, for this experiment, this would look like: = 10.8/4.22 = 2.55924 t = 2.56 To use this t-value, we must compare it to the critical t-value for D.F. = 9. If our calculated value is > critical value in table, we can reject the null hypothesis. Assuming we use p< .05 or 5% (as in Chi-Square): Our calculated is 2.56, so Critical < Calculated We know that the null hypothesis of no difference between the means can be rejected, but that does not mean our hypothesis is either supported or rejected. We originally hypothesized that: Tooth decay is greater in communities without fluoride. Xf < Xnf From our data (% of population with tooth decay), we found that nf = mean of 22.4, f= mean of 11.6 We now know that 1. The means are significantly different; reject null 2. Difference between two means matches our hypothesis. Conclusion: We found that communities without fluoridated water had a greater percentage of the population with tooth decay than communities with fluoridation (t - 2.56, d.f.=9, p<.05) ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our International Baccalaureate Psychology section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related International Baccalaureate Psychology essays

  1. Psychology Critical Analysis Questions

    Best (1986) wants to remind us that there is no single theory of cognition that is shared by all psychologists. There are two of these in this perspective. The first one is that scientific methods involving experiments and hypothesis testing are in the best way to gather knowledge about human cognition, and

  2. Ethics In Psychology

    The general ethical stance on animal testing is that it is permissible as long as the scientific benefits outweigh the costs in animal life. Scientists and governments state that animal testing should cause as little suffering to animals as

  1. How Psychology Could Help Reverse the Trend in Obesity

    but there are a number of snowball mechanisms that lead to weight gain mostly centred about body image: mainly negative experiences with physical activity and sport dictating an indoor life and may even be discriminated by their doctor and other health-care staff who may themselves feel disgusted by fat patients (Maddox et al., 1968).

  2. Psychology IB Abnormal Notes and Essay Plans

    do our thinking styles affect the levels of neurotransmitters in our brains? We do not know for sure. 4. There is a wealth of evidence to support the idea that (CBT) Cognitive Behavioural Therapy helps people to become well. This is a form of psychotherapy that challenges a personâs beliefs, helping them to rationalize distorted cognitions.

  1. Psychology IB Abnormality Notes

    Evaluation point: 1. Drug treatments work, which supports the idea of neurotransmission imbalance. Abnormal level of neurotransmitters may not cause depression, According to Burns, there is inadequate evidence to support the idea that this is the cause. Lacasse and Leo agree, stating that the brain is far more complex and

  2. Anger management as a method of treating offenders

    Other benefits of this system are ease of administration, the use of immediate or frequent reinforcement (tokens) while teaching delayed gratification (holding tokens until trade-in time), lack of boredom or satiation for the prisoner due to the availability of a variety of back-up reinforcers, and lack of competition between other prisoners as they compete only against themselves.

  1. A Long Way Gone: Memoirs of a Boy Soldier by Ishmael Beah--A Psychological Analysis ...

    Everyone was given the choice, or so the Lieutenant claimed it was a choice. Lieutenant Jabati uses every tactic that is available to him to recruit the group of people that are in his presence. He claims that the children must join out of necessity, out of fear, out of

  2. Of Dreams and Reality: A paper on hypnosis and dream analysis

    These friends (which we could say represents our unconscious) symbolized our innermost innate selves free from social conformity and everyday pressures. It was, therefore, an attempt at communicating with our covert desires and emotions. As Ernest Hilgard would put it, the process of hypnosis is tantamount to a hidden observer wherein dissociation is present between the unconscious and the conscious.

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work