Table 2.
Comparison between the pH of different samples measured with different devices.
| Sample | Potentiometer | Scanner | Error | Portable Instrument | Error | P-value |
|---|---|---|---|---|---|---|
| Lemon dressing | 2.35 | 2.19 | 0.16 | 2.31 | 0.04 | 0.016 |
| Tonic | 2.49 | 2.59 | 0.10 | 2.39 | 0.10 | 0.027 |
| Orange soft drink | 2.75 | 2.83 | 0.08 | 2.67 | 0.08 | 0.044 |
| Orange fizzy drink | 2.91 | 2.98 | 0.07 | 2.92 | 0.01 | 0.035 |
| Blackberry liqueur | 2.91 | 3.08 | 0.17 | 2.95 | 0.04 | 0.107 |
| Lemon fizzy drink | 3.30 | 3.43 | 0.13 | 3.34 | 0.04 | 0.021 |
| Cola fizzy drink 1 | 2.85 | 2.78 | 0.07 | 2.89 | 0.04 | 0.055 |
| Cola fizzy drink 2 | 2.75 | 2.84 | 0.09 | 2.71 | 0.04 | 0.024 |
| Vinegar | 3.03 | 2.99 | 0.05 | 3.09 | 0.06 | 0.616 |
| White wine | 3.35 | 3.29 | 0.05 | 3.36 | 0.02 | 0.117 |
| Mandarin juice | 3.57 | 2.44 | 0.13 | 3.52 | 0.04 | 0.228 |
| Pineapple juice | 3.68 | 2.69 | 0.01 | 3.67 | 0.02 | 0.633 |
| Tomato juice | 4.17 | 4.23 | 0.06 | 4.11 | 0.05 | 0.354 |
| Orange juice | 3.49 | 3.45 | 0.04 | 3.56 | 0.07 | 0.869 |
| Apple juice | 3.20 | 3.10 | 0.10 | 3.16 | 0.04 | 0.191 |
| Peach juice | 4.01 | 4.12 | 0.12 | 4.06 | 0.05 | 0.208 |
| Grape juice | 3.78 | 3.70 | 0.08 | 3.68 | 0.10 | 0.660 |
| Tinned gherkins | 2.89 | 2.72 | 0.17 | 2.91 | 0.02 | 0.033 |
| Tinned artichokes | 3.80 | 3.78 | 0.02 | 3.72 | 0.08 | 0.021 |
| Tinned mushrooms | 4.96 | 4.86 | 0.10 | 5.02 | 0.06 | 0.296 |
| Tinned soya | 3.97 | 4.07 | 0.10 | 4.05 | 0.08 | 0.558 |
| Tinned olives | 4.07 | 4.14 | 0.07 | 4.09 | 0.02 | 0.183 |
| Tinned carrots | 3.76 | 3.72 | 0.04 | 3.78 | 0.02 | 0.265 |
| Beer | 4.16 | 4.30 | 0.14 | 4.24 | 0.08 | 0.176 |
| Alcohol-free beer | 4.50 | 4.25 | 0.25 | 4.38 | 0.12 | 0.116 |
| Black tea | 4.93 | 5.08 | 0.15 | 5.21 | 0.28 | 0.068 |
| Decaffeinated coffee solution | 5.67 | 5.33 | 0.34 | 5.42 | 0.25 | 0.311 |
| Skimmed milk | 6.70 | 6.59 | 0.11 | 6.61 | 0.09 | 0.822 |
| Sparkling mineral water | 5.30 | 5.29 | 0.01 | 5.36 | 0.06 | 0.292 |
| Mineral water 1 | 7.17 | 7.19 | 0.02 | 7.14 | 0.03 | 0.149 |
| Mineral water 2 | 7.29 | 7.66 | 0.36 | 7.35 | 0.06 | 0.217 |
| Mineral water 3 | 7.59 | 7.58 | 0.01 | 7.62 | 0.03 | 0.892 |
| Tap water | 7.85 | 7.97 | 0.12 | 7.96 | 0.11 | 0.294 |
| Toothpaste solution (1:3) | 7.22 | 7.31 | 0.09 | 7.36 | 0.14 | 0.297 |
| Mouthwash | 7.30 | 7.53 | 0.23 | 7.43 | 0.13 | 0.178 |
| Diluted washing-up liquid | 7.30 | 6.87 | 0.42 | 7.02 | 0.28 | 0.299 |
| Contact lens saline solution | 7.54 | 7.35 | 0.20 | 7.40 | 0.14 | 0.442 |
| Bleach solution (1:5) | 8.99 | 2.52 | 6.47 | 3.42 | 5.57 | 0.030 |
| Sodium bicarbonate saturated solution | 8.44 | 8.37 | 0.07 | 8.30 | 0.14 | 0.527 |
| Ammonia solution (1:10) | 11.04 | 11.46 | 0.42 | 11.58 | 0.54 | 0.312 |
| Average error: | 0.13 | Average error: | 0.09 | |||