A jelly-baby manufacturer is aware that many people like the red jelly babies best, but wants to know if this is the same in the North and South Island. From a survey, we have the following data:

North Islanders: Of 310 North Islanders surveyed, 200 prefer red jelly babies.

South Islanders: Of 180 South Islanders surveyed, 70 prefer red jelly babies.

Say that the true proportion of North Islanders who prefer red jelly babies is p₁ and the true proportion of South Islanders who prefer red jelly babies is p₂.

If our null hypothesis is H₀: p₁ - p₂ = 0 and our alternative hypothesis is H_a: p₁ - p₂ 0, what is the z test statistic for testing the difference p₁ - p₂?

Calculate this z test statistic and enter your answer, correct to 3 decimal places, into the box below. (Use Excel to perform the whole calculation without rounding intermediate results.)