Answer:
There is not enough evidence that their efforts have paid of. The stations are not showing less leakage.
Step-by-step explanation:
The population proportion of service station that has gas storage tanks that leak to some extent is <em>p</em> = 0.40.
To test whether this proportion has decreased the hypothesis can be defined as:
<em>H</em>₀: The proportion of service stations whose tanks leak has not decreased, i.e. <em>p</em> ≥ 0.40.
<em>H</em>ₐ: The proportion of service stations whose tanks leak has decreased, i.e. <em>p</em> < 0.40.
Given:
<em>n</em> = 27
<em>X</em> = number of service stations whose tanks leak = 7
The sample proportion of service stations whose tanks leak is:

Assume that the significance level of the test is <em>α </em>= 5%.
The test statistic is:

The value of test statistic is -1.49.
Decision rule:
If the <em>p</em> value is less than the significance level the null hypothesis will be rejected and vice-versa.
The <em>p</em>-value of the test statistic is:

The <em>p-</em>value = 0.0681 > <em>α</em> = 0.05.
Thus, the null hypothesis is not rejected at 5% level of significance.
<u>Conclusion</u>:
As the null hypothesis was not rejected at 5% level of significance, it can be concluded that the proportion of service stations whose tanks leak has not decreased.