You are a research scientist studying bioluminescent bacteria (bacteria that can glow). You grow several plates of bacteria and give them a special chemical that you hypothesize will increase their luminescence, or brightness. You turn off the lights and use a device called a photometer to measure the light levels (in lumens) coming from each plate. You collect the following data:
Plate 1: 7 lumens, 6 lumens, 13 lumens
Plate 2: 4 lumens, 5 lumens, 7 lumens
Plate 3: 3 lumens, 6 lumens, 7 lumens
Plate 4: 5 lumens, 5 lumens, 8 lumens
Which of the following pieces of data is likely an outlier?