data analysis; graphs

• a summary table is a way of representing data. it is the results descriptive stastistics section of a report. e.g. table showing the mean number of words spoken and standard deviations for the redbull condition and the water condition. mean: redbull - 119,water - 96. the mean values suggests that there were more words spoken on average from the energy drink suggesting people are more talkative when having energy drinks. SD redbull - 53.8, SD water - 35.8. the SD is higher for redbull meaning there was a larger spread of scores which suggests that not all participants were equally affected
• data can be represented visually using a suitable graphical display so the difference in mean values can easily be seen
• bar charts are used when data is divided into categories which is known as discrete data. the example for energy drink example would be that the categories are our two conditions (redbull and water as x axis) and the frequency (of words spoken) in the y axis. bars are seperated on a bar chart to denote that we are dealing with seperate conditions
• scattergrams depict the assocations between co variables. either the co variable occupies the x axis and the other the y axis and each point on the graph corresponds to the x and y position of the co variables
• in a histogram the bars touch each other to show the data is continuous rather than discrete (bar charts). the x axis is made up of equal sized intervals of a single category. the y axis represents the frequency within each interval. if there was a zero freuquency for one of the intervals, the interval remains but without a bar
• line graphs represent continuous data and use points connected by lines to show how something changes in value for instance over time. typically, the IV is plotted on the x axis and the DV on the y axis
• a normal distribution is when you measure certain variables and the frequency forms of bell shaped curve which is symmetrical. within a normal distribution, most people are located in the middle area of a curve with very few people at the extreme ends. the mean, median and mode all occupy the same mid point of the curve
• some data sets derived from psychological scales may produce skewed distributions which is when distributions appear to lean to one side]
• a postive skew is where most of the distribution is concentrated towards the left of the graph resulting in a long tail on the right. the mode remains at the highest point (the peak). the median then comes next. the mean is dragged across to the right as extreme scores affect the mean.
• a negative skew is a type of distribution in which the long tail is on the negative side of the peak and most of the distribution is concentrated on the right. the mean is pulled to the left (due to the lower scorers who are in the majority). the mode is at the peak and the median is in the middle