Answer:
Internal validity.
Explanation:
Internal validity is the study in which trust relationship is build between treatment and outcome. This relationship is known as <em>cause-and-effect. </em>
In this type research, the studies are based on whether the finding is questionable or not. The research which can overrule the possibility of alternative explanations of our findings is internally valid.
The threats of internal valid study are:
- <u>Natural Improvement </u>
- <u>Maturation</u>
- <u>Historical Events</u>
- <u>Placebo effects</u>
- <u>Nonspecific effects</u>.
So, the correct answer is 'Internal validity'.
It contained iron furnaces<span />
Answer:
The world population increased from 1 billion in 1800 to 7.7 billion today. The world population growth rate declined from 2.2% per year 50 years ago to 1.05% per year.
