Encouraging individuals to recycle more effectively is a key challenge for local authorities, and subtle cues can often make a significant difference. A behavioral psychologist investigated whether placing a small green leaf sticker on a general waste bin would reduce the amount of recyclable waste incorrectly discarded in it.
She conducted an experiment using a sample of 11 households obtained through opportunity sampling. For one week, participants recorded the number of dry recyclable items (plastic bottles, cardboard packaging, aluminum cans, etc.) incorrectly thrown into their general waste bin in-between collections. The following week, a prominent green leaf sticker was placed on the lid of the general waste bin, and the same householders again recorded the number of recyclable items incorrectly discarded inside it. The data is presented in the table below.
| Household | Number of recyclable items thrown into general waste bin during one week | |
|---|---|---|
| Without green leaf sticker | With green leaf sticker | |
| A | 15 | 11 |
| B | 24 | 18 |
| C | 11 | 8 |
| D | 30 | 22 |
| E | 18 | 15 |
| F | 22 | 23 |
| G | 9 | 5 |
| H | 27 | 19 |
| I | 16 | 12 |
| J | 21 | 16 |
| K | 14 | 13 |
Calculate the mean for the number of recyclable items thrown into the general waste bin in the week without the green leaf sticker. Show your workings and write your answer to three significant figures.