What do research interactions and main effects mean?  What do interactions reveal that main effects cannot?

Early 18th century british industries were generally small scale and relatively unsophisticated. most textile production, for example, was centred on small workshops or in the homes of spinners, weavers and dyers: a literal ‘cottage industry’ that involved thousands of individual manufacturers. such small-scale production was also a feature of most other industries, with different regions specialising in different products: metal production in the midlands, for example, and coal mining in the north-east.two illustrations of 18t