How do I solve these questions?
Use the trial-by-trial data to answer these questions. Question Answer Status Standard deviation of the number of distractors ($1): Check answer Hint Not yet answered correctly (The difference between your answer and the correct value must be less than 0.01.) Standard deviation of the reaction times ($2): Check answer Hint (The difference between your answer and the correct value must be less than 0.01.) Not yet answered correctly Correlation between the number of distractors and reaction times: (The difference between your answer and the correct value must be less than 0.01.) Check answer Hint Not yet answered correctly b: (The difference between your answer and the correct value must be less than 0.01.) Check answer Hint Not yet answered correctly Mean of the number of distractors: (The difference between your answer and the correct value must be less than 0.01.) Check answer Hint Not yet answered correctly Mean of the reaction times: (The difference between your answer and the correct value must be less than 0.01.) Check answer Hint Not yet answered correctly a: Check answer Hint Not yet answered correctly (The difference between your answer and the correct value must be less than 0.01.) Hint: Compute the standard deviation of the number distractors s al target absent trialsv Questions What methods did we employ in this experiment? On each trial, you saw a number of distractor stimuli, green squares and blue circles. On half the trials, a green circle was also shown. your task was to quickly report the presence or absence of the target green circle. There are two independent variables in this experiment: The number of stimuli and whether the target green circle was shown. The dependent variable is the time it took you to correctly identify whether the green circle was present or absent. What do we predict participants will do? Why? There are a number of predictions: (1} You will generally be faster to identify the presence or absence of the target green circle when there are fewer distractors; (2) you Wl" generally be faster to respond conectly on trials in which the green circle is present than on trials in which the green circle is absent; and (3) the difference in response time between target present and target absent trials Wl" be greater as the number of distractors increases. In order to correctly identify the presence or absence of the target, you need to process feature conjunctions. That is, some of the distractors are green, some are blue, some are circles, and some are squares. So, you can't look forjust one feature; instead, you need to look for a specic combination: green plus circle. This requires attention and therefore takes time. Some theories of visual perception suggest that the increased time is almost linearly related to the number of distractors. In the questions below, you will calculate the terms of the best tting straight line for one of the search conditions: when the target was absent. You will be estimating the slope and intercept of a straight line that follows the formula: Reaction Time = a + b {Number cfdistractors) where a is the intercept and b is the slope. To complete the assignment you Ml! not need the data from trials where the target was present Formulas To calculate the slope (b), you need to rst calculate the standard deviation of the number of distractor values (5,), the standard deviation for the reaction time values (52), and the correlation between the scores (r) These values are then combined to compute the slope: s b = fl . 51 To calculate the intercept, rst compute the mean of the number of distractor values (i1) and the mean of the reaction time values (i2). The intercept is then computed with this formula: 0. 2 f2 bfl. Answer the questions using the data below. You will often nd it helpful to sort the data and calculate values using a spreadsheet such as Miuoso Exce|, Sheets from Google apps, Open Ofce, or Numbers (Mac only). To import the data into a spreadsheet select and copy all the cells in the trial-bytrial data table below and then paste them into an open page of the spreadsheet. On each trial, your task was to report whether there was a green circle or not. Each row below indicates the characteristics of each trial. The second column indicates whether the target was present or not. The third column indicates the number of distractor elements, and the last column gives the time between the onset of the display and your key press. Trial Target Number of distractors Reaction time (ms) Present 30.0 422.0 Present 9.0 522.0 Present 24.0 1932.0 Present 14.0 599.0 Present 17.0 599.0 Present 30.0 1515.0 Absent 18.0 719.0 Present 28.0 1073.0 Present 10.0 1167.0 Absent 25.0 794.0 11 Present 4.0 4388.0 12 Absent 10.0 2219.0 13 Present 15.0 1417.0 14 Absent 29.0 886.0 15 Absent 4.0 453.0 16 Present 28. 568.0 17 Absent 28.0 431.0 18 Absent 26.0 1409.0 19 Absent 25.0 988.0 20 Absent 8.0 2204.0 21 Absent 5.0 1136.0 22 Absent 19.0 720.0 23 Absent 6.0 845.0 24 Absent 16.0 845.0 25 Absent 29.0 1008.0 26 Absent 7.0 683. 27 Absent 14.0 903.0 28 Absent 7.0 839.0 29 Present 11.0 836.0 30 Present 7.0 847.0 31 Present 17.0 893.0 32 Present 25.0 1045.0 33 Present 7.0 740.0 34 Present 29.0 896.0 35 Present 16.0 2698.0 36 Absent 9.0 1267.0 37 Present 24.0 1017.0 38 Present 21.0 996.0 39 Absent 24.0 946.0 10 Absent 17.0 888.0
