African Borders as Sources of Natural Experiments Promise and Pitfalls

Africa’s arbitrary country borders have been seized upon as sources of “natural experiments”: having randomly assigned people to different country treatments, differences in outcomes on either side of the border can then be attributed to the institutions, demographics, or policies put in place in each country. While methodologically attractive, the use of African borders as sources of natural experiments presents several potential pitfalls. We describe these pitfalls—some common to all studies that employ jurisdictional boundaries, some unique to African borders—and offer guidelines for overcoming them. We conclude that African cross-border studies can provide research advantages similar to well-executed comparative case studies, but that they frequently offer weaker inferential leverage than is claimed

KSPC (Keystrokes per Character) as a Characteristic Of Text Entry Techniques

KSPC is the number of keystrokes, on average, to generate each character of text in a given language using a given text entry technique. We systematically describe the calculation of KSPC and provide examples across a variety of text entry techniques. Values for English range from about 10 for methods using only cursor keys and a SELECT key to about 0.5 for word prediction techniques. It is demonstrated that KSPC is useful for a priori analyses, thereby supporting the characterisation and comparison of text entry methods before labour-intensive implementations and evaluations