# Lab 3 u2013 Worksheet.pdf - Lab 3 u2013 Worksheet Today...

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Lab 3 – Worksheet Today we are going to measure the size of your illusion using the method of constant stimuli. In this method, we are going to keep the length of the reference line constant (i.e., the line on the left will always be 160 pixels). On each trial you will see different lengths of the line on the right, and you need to decide whether the line on the right appears longer or shorter than the reference line. 1) In the online experiment you viewed 13 different line lengths. Each line length was viewed 4 times. At the end of the experiment, the computer displayed the mean % of the time you said “longer” for each of the line length. Copy those means into the chart below. Line Length (dpi) Mean % of the time you said Longer 150 0 155 0 160 0 165 0 170 0 175 0 180 0 185 50 190 75 195 100 200 100 205 100 210 100
2) Create a graph to calculate the size of your illusion (you can do this by hand or by using the excel/google spreadsheets template). Please paste your graph below. 3) Provide a definition of the Point of Subjective Equality (PSE) and the Point of Objective Equality (POE).